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G—ééé4e.
ELECTRO-CHEMISTRY.
INORGANIC .
A"
G9°
GORE ,LL.D.,
Aut/zor of
Th e Art o f Sc ien tifi c D iscov e ry“ Th e Art o f E lectro -M eta llu rg y ,
Th e Pr in cip les an d Practi ce o f E lectro -Depo'
s i tion ,
Th e S cien tifi c Bas i s o f Nation al Prog ress ,etc ., etc .
S E C O N D E D I T I O N .
LONDON
THE ELECTRICIAN PR INT ING PUBLISHING COMPANY (LIMITED),I, Salisbury Court, Fleet Street, E C.
NEW YORK
W.J.JOHNSTON, “ THE ELECTRICALWORLD,
168 - 1 77 , Po tterBuild ing .
INDEX TO CONTENTS.
ACETATE OP CERIUM , ELECTROLYSIS OPLEAD
ALKAL I METALS ELECTRO DEPOSITEDALLOYS
,ELECTROLYSIS OP ? .OP ZINC AND COPPER
,ELECTRo -DEPOSI
T ION OP
OP Z INC , COPPER, AND N ICKEL , ELECTRODEPOS ITION OPALUM IN IUM , ELECTROLYS IS IN THE METALLURGY OP
SEPARATIONAMMON IA , ELECTROLYSIS OPFIRST ELECTROLYSEDAMMON IUM AMALGAM , ELECTROLYTIC
CARBONATE,ELECTROLYSIS OP
CHLORIDESEPARATION OP ?FLUORIDE , ELECTROLYSIS OPNITRATE
SULPHATEAMMON IO CHLORIDE OP MAGNESIUM , ELECTRO
LYSIS OP
ANALYSIS OP COPPER ORES BY ELECTROLYS IS .ANODE
,MEAN ING OP THE
ANODES , INSOLUBLE COATINGS ONOP CARBON , ELECTROLYSIS W ITHANTIMON IATE OP POTASS IUM , ELECTROLYSIS OPANTIMONY,ELECTRo-DEPOSITION OP EXPLOSIVE .SEPARATION OPTERBROMIDE , ELECTROLYSIS OPTERCHLORIDETERPI.UORIDETERIODIDETEROXIDETERSULPH IDE
AQUEOUS AMMON IAARGENTIC CHLORATECHLORIDEFLUORIDENITRATEPEROX IDESULPHATE
ARGENTO POTASS IC CYAN IDESOD IC SULPHATE
ARSEN IC, SEPARATION OPACID,ELECTROLYSIS OP .TERCHLORIDE
,ELECTROLYS IS OP
ARSEN IDE OP HYDROGEN , ELECTROLYTI C SEPARATION OP ..
AURIC TERCHLORIDE,ELECTROLYSIS OP
AURO CYANIDE OP POTASSIUM
C Q C C D C
B ARIUM , SEPARATION OPHYDRATE , ELECTROLYSIS OP
B ATTER IES , VOLTAICB ATTERY PROCESS OP ELECTRO-DEPOS ITIONB IPLUORIDE OP TIN , ELECTROLYSIS OP .
B ISMUTH , SEPARATION OPCHLORIDE
,ELECTROLYSIS OP .
CYAN IDEFLUORIDEIOD IDEN ITRATE
OX IDEPEROX IDE,ELECTROLYTICFORMATIONOP
B ISULPHIDE OP CARBONBORATE OP SOD IUM , ELECTROLYSIS OP ..
BORON , SEPARATION OPCOMPOUNDS, ELECTROLYSIS OP
O I D O C O O O O O
1 1 31 1 91 1 6
1 3 1
2
1 32
I 33I 331 3 1
I 331 32
I 34
1 1 485
41 4
60
1 3 1
7 3
7 3
7 2
7 1
7 1
7 4
7 5
P
BROM IDES, CHLORIDES , AND IOD IDES , ELECTROLY'SIS OP
BROM IDE OP CADMIUM, ELECTROLYSIS OPIOD INEBROM INE, ELECTROLYTIC SEPARATION OP .
ELECTROLYS IS OP OX IDES OPBRUGNATE LLI
’S EXPERIMENTS IN ELECTRO
BRUGNATELLI FIRST DEPOSITS ZINCCADM IUM ’ SEPARATION OF o o o o o o o o o o o c c c c c e o n -n o
COMPOUNDS , ELECTROLYTIC ANALYSISSELF-DEPOSI TION OP
CAES IUM , SEPARATION OPCALCIUMCARBON
Q O I C O O O O I O O O
S ILVER
O O O O O O O O O O O O O O O O O O O O
C O O P O O
0
nANODES , ELECTROLYSIS W ITHCARBONATE OP AMMON IUM , ELECTROLYS IS OPPOTASSIUMRUB ID IUMS ODIUMSTRONTIUM
CARBONIC ANHYDRIDECATHODE , MEAN ING OP THE TERMCATHODES , CORROSION OPCEASELESS MOLECULAR MOTION THEORY OPVOLT 'A IC ACTION
CERIUM , SEPARATION OPCHEM ICAL ACT ION , ELECTRICAL THEORY OPCORROSION , ELECTROLYTIC BALANCE
CHLORIC ACIDCHLOR IDES
,BROM IDES , AND IOD IDES ELECTROLYSIS OP
OP ALUM IN IUM AND SOD IUM,ELEC
TROLYSIS OP
AMMON IUM , ELECTROLYS IS OPARSEN IC , ANTIMONY, AND TIN,ELECTROLYSIS OPBARIUM , ELECTROLYS IS OPB ISMUTHCADM IUMCAES IUMCALC IUMCERIUMCOBALTCOPPERIRONLEADLITH IUMMAGNESIUM AND AMMON IUM
,ELEC
MANGANESE, ELECTROLYSIS OPMERCURYN ICKELPALLAD IUMPLATINUMPOTASSIUMRUB ID IUMSI LVERSOD IUMSTRONTIUMSULPHURTIN , ELECTROLYSIS OPZINCELECTROLYTIC SEPARATION OP
INDEX.
PAGECHLORINE , ELECTROLYS IS OP OX IDES OP 43CHROM IUM , DEPOSITION OP 96ELECTROLYTIC ANALYSIS OP COM
POUNDS OPCIRCUMSTANCES WH ICH APPECT THE AMOUNT OP
ELECTRO CHEM ICAL ACTION . 9-1 0
WH ICH APPECT THE K IND OPCOBALT, ELECTRO~DEPOSITION OP
COMPOUNDS , ELECTROLYTIC ANALYSIS OPCHLORIDE , ELECTROLYSIS OPCYAN IDEFLUORIDESULPHATEPEROXIDE, ELECTROLYTIC FORMATION OP
COMPOUNDS OP CADM IUM , ELECTROLYTIC ANAL.OP I 10
CHROM IUMCOBALTGLUCINUMIND IUMIRONLEADMANGANESEMOLYBDENUMN ICKELTHALLIUMTINURAN IUMVANAD IUMZINC
CONDUCTIVITY OP LIQU IDS .CONDUCTION IN ELECTROLYTES W ITHOUT DECOM
POSITION 79COPPER, SEPARATION OF 0 C 0 O O 0 0 O O O 0 t 0 0 0 0 0 O 0 O O O O 0 7 8ELECTROLYTIC PURIPICAT ION OP 82
ETCHED BY ELECTROLYTIC ACTION . 83REPINED BY 83N ITRIDE , ELECTROLYTIC FORMATION OP 79ORES ANALYSED BY ELECTROLYS IS 85AND T IN ALLOYS , SEPARATION OP 108ZINC
Z INC , AND ICREL ALLOY, EDEPOSITION OPCORROSION OP CATHODESCRYSTALS OP TIN FORMED BY ELEC TROLYSI SCRUICRSHANR
’S EXPERIMENTS
CUPRIC CHLORIDE, ELECTROLYS IS OPFLUORIDEN ITRATESULPHATE
CUPROSO POTASS IC CYAN IDE , ELECTROLYSIS 0CURRENT , STRENGTH
RELATIVE AMOUNTS OP, PRODUCED BYDIPPERENT METALS
CYAN IDE OP BISMUTH , ELECTROLYSIS OP .CAESIUMCOBALTCOPPERANDPOTASSIUM,ELECTROL OPGOLDPALLADIUM , ELECTROLYSIS OP .POTASSIUM§ILYERAND POTASS IUM , ELECTROL OPINC
DAVY’S DISCOVERY OP THE ALRALI METALSDECOMPOSA BILITY OP ELECTROLYTES ..DEPINITE ELECTRO-CHEM ICAL ACTIONDEPIN
‘
IT ION OPDENSITY OP CURRE NTELECTRo-DEPOS ITSDEPOS ITS , CIRCUMSTANCES APPECT ING KIND OP
C IRCUMSTANCES APPE CTING AMOUNTDESILVER ISING LEADD IDYM IUM , SEPARATION OPD ISCOVERY OP THE VOLTAIC BATTERY
ALKALIDEPINITE ELECTRO CHEM ICAL
D I STRIBUTION OP CURRENT IN ELECTROLYTESD IVIDED ELECTROLYSIS
O O Q I Q O O O O O O O O O O O
O O O Q O O Q O O O O O O O O C O O O C Q O .
Q O O O O Q O O O O O C O O O O O O O O O O Q .
Q O O O O O O O Q O O O O Q O O O O
O O Q O O O O O O O O O O O O O O O Q Q O O
IND IVIDUAL SUBSTANCESRELATIONS OP , To HEAT .SECONDARY EPPECTS OP
V ISIBLE PHENOMENA OPELECTROLYTES
,D ISTRIBUTION OP CURRENT INANALYSIS FIRST SUGGESTEDBALANCE OP CHEM . CORROSION .AND VOLTAIC ACTION , CONNECTION BETWEENANDVOLTAICACTION,
DIST INCT ION
DEPOSITS, PURI TY OPD IPPUSION OP LIQU IDSETCHING OP
MOVEMENTS OPSEPARAT ION OP
M NSI'ER FIRSTEXPLOSIVE ANTIMONY, ELECTRo-DEPOSITION OP..
0 0 0 0 0 0
FERROUS
ELECTRICAL THEORY OP CHEM ISTRY 24
ELECTRO-CHEM ICAL ACTION , DEPINIT ION OP 3CH IEP COND ITIONS OP 3THEORIES OF 20-21
ELECTRO CHEM ISTRY OP IND IVIDUAL SUBSTANCES 32
ELECTRODES,MEAN ING OP THE TERM 4
-5POLARISATION OP 1 6
UN UAL ELECTRIC ACTION AT 1 6
ELECTRO-GILD ING PON S ILVER FIRST OBSERVED 2
ELECTROMOTIVE FORCE 25-26
ELECTROLYSIS , D IVIDED 1 5DEPENDENCE OP, UPON LIQU IDD IFFUSION 1 8
INPLUENCE OP MAGNETISM UPON 10TEMPERATURE 1 0
RELATION OP,TOCHEMICALACT ION I I
LIM ITS OP 7
7
32
I 9I3
4
30
1 42
30
I 2
FARADAY’S D ISCOVERY OP DEPINITE ELECTROLYTIC ACTION
FERRATE OP POTASS IUM , ELECTROLYSIS OPFERRI-CYAN IDE OP POTASS IUMFERRIC CHLORIDEFERRO-CYAN IDE OP IRON
POTASSIUMCHLORIDESULPHATE
FLUORIC ACIDFLUORIDE OP ALUM IN IUM
AMMON IUMANTIMONYBISMUTH
COBALTCOPPERGOLDLEADLITHIUMMANGANESEN ICKELPALLAD IUMPOTASSIUMS ILVERSODIUMSTRONTIUMT INURAN IUM
FLUORINE,ELECTROLYTIC SEPARATION OP ?
GALLIUM , SEPARATION OPGERBOIN
’S EXPERIMENTS
GLUC INUM,SEPARATION OP
GOLD , SEPARATION OPGOLD FLUORIDE, ELECTROLYTIC FORMATION OP 68
GOLDING BIRD ’s EXPERIMENTS 3
INDEX.
PAGEHEAT ITS RE LATION To ELECTROLYSIS 19
-20
HENRY’s EXPERIMENTS 2
R ISINGER AND BERZ ELI US D ISCOVER ELECTROH ISTORY OP ELECTRO-CHEM ISTRYHYDRATE OP BARIUM , ELECTROLYSIS OPPOTASS IUM
SOD IUMHYDRIC SULPH IDE , SEPARATION OP , BY ELECTROLYSIS
HYDRIDE OP S I LICON , SEPARATION OP, BY ELECTROLYSIS
HYDRIOD IC AC ID , ELECTROLYS IS OP . 44HYDROBROM IC AC ID 44HYDROCHLORIC 42
HYDROFLUORIC 40-42
HYDROGEN,ELECTRO DEPOSITION OP 33IN ELECTROLYTIC DEPOSITS 34EXPLOSIVE ANTIMONY 35PEROX IDE
,ELECTROLYSIS OP 37
INDIULI’ SEPARATION OF O O 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 105COMPOUNDS, ELECTROLYTIC ANALYS IS OP 105INSOLUBLE COATINGS ON ANODES . 1 4IOD IC ACID , ELECTROLYSIS OP 44IOD IDES
,BROM IDES , AND CHLORIDES, ELECTROL OP 4 5IOD IDE OP B ISMUTH 6 1
PALLAD IUM 64POTASS IUM 1 29IOD INE, SEPARATION OP 44ELECTROLYSIS OP OX IDES 45IONS,MEANING OP THE TERM 4TRANSPORT 1 9
IRID IUM , SEPARATION OP . 62IRON 9 1:COMPOUNDS , ELECTROLYTIC ANALYSIS OP 94CHLORIDE , ELECTROLYS IS OP 9 2
FERROCYAN IDE 94SULPHATE 9 3RENDERED BRITTLE BY ELECTROLYS IS 35ISOLATION OP FLUORINE ? 40
LANTHANUM , SEPARATION OP 1 1 5LAW OP DEF IN ITE ELECTROLYTI C ACTION 2-1 0
LEAD,SEPARATION 1 00
COMPOUNDS , ELECTROLYTIC ANALYSIS OP . 1 03ACETATE , ELECTROLYS IS OP . 1 01
CHLORIDE 1 01
FLUORIDE 0 0 0 0 0 0 l 0 0 0 0 0 0 0 I O !
N ITRATE I oo
DES ILVERISED BY ELECTROLYSIS ‘I 1 03PEROX IDE, ELECTROLYTIC FORMATION OP 2-102
LIM ITS 7LIQU ID D IPPUSION, RELATION OP, TO ELECTRO
LIQU ID ELECTRODES, MOVEMENTS OPLIQU IDS, EL ECTRIC CONDUCTIV ITY OPLITH IUM , SEPARATION OF 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
MAGNES IUM , SEPARATIONELECTRo-METALLURGY OPMAGNETISM , ITS EPPECT UPON ELECTROLYSIS .
MANGANESE, SEPARATION OPCOMPOUNDS, ELECTROLYTIC ANAL .OPCHLORIDE , ELECTROLYSIS OP .FLUORIDESULPHATEPEROX IDE , ELECTROLYTIC FORMATION OPMEASUREMENT OP CONDUCT ION RESI STANCE .ELECTROMOTIVE FORCEQUANTITY OP CURRENTSTRENGTH
MERCURY , SEPARATION OPMERCURIC CHLORIDE , ELECTROLYSIS OPN ITRATEPoTASSIo-CYAN IDE , ,
ALLO-CHROMYMETALS, SELP DEPOS ITION OPM INERALS, DECOMPOS ITION OP , BY ELECTROLYSISMODES OP PRODUCING VOLTAIC CURRENTS
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
MOLECULAR MOTION THEORY OP VOLTAIC ACT IObMOLYBDENUM , SEPARATION OP .
COMPOUNDS,ELE CTROLYT ICALANAL.OMOLYBD IC ACID , ELECTROLYSIS OPMOVEMENTS OP MERCURY BY ELECTROLYSIS 2
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 .
0 0 0 0 0 0 0 0 0 0
0 . 0 0 0 0 0 0 0 0
O . 0 . 0 0 0 0 0 .
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 .
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0
0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 .
OSM IUM , SEPARATION OP .OSM IC AC ID , ELECTROLYSIS OP .
OX IDE OP BISMUTHOX IDES OP BROM INE , ,
CHLORINEIOD INEN ITROGEN , ,PHOSPHORUS
OXYGEN,SEPARATION OP
OZ ONE
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 .
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 l
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
PAETz AND VAN TROOSTVIK'
S EXPERIMENTSPALLAD IUM
,SEPARATION OPCHLORIDE, ELECTROLYSIS OPCYAN IDEIOD IDEN ITRATE
FLUORIDE,ELECTROLYTIC FORMATIOOP
PEROXIDEPASSIVE STATE OP METALSPERCHLORATE OP S ILVER, ELECTROLYSIS OP .
PERCHLORIDE OP IRONPEROXIDE OP B ISMUTH , ELECTROLYTIC FORMATION OF
0 0 0 0 0 0 0 !
0 0 0 0 0 0 0 0 0 0 0
PLUMBATE OP POTASH , ELECTROLYSIS OP .PLUMB IC ACETATECHLORIDE
0 0 0 0 0 0 0 !
N ICKEL,SEPARATION OPCOMPOUNDS, ELECTROLYTIC ANALYSIS OPCHLORIDE
,ELECTROLYSIS OP
FLUORIDEN ITRATESELENATESULPHATEZINC
,AND COPPER ALLOYS, ELECTRODEPOS ITION OP I
N ICHOLSON AND CARLISLE DECOMPOSE WATERN ITRATES , ELECTROLYSIS OPN ITRATE OP AMMON IUM , ELECTROLYSIS OP
BARIUMB ISMUTHCERIUMCOPPERLEADMERCURYN ICKELPALLAD IUMPOTASSIUM
n nS ILVER nN ITR IC ACID , ELECTROLYSIS OP
NITRIDE OP COPPER , ELECTROLYTIC FORMATION OPN ITROGEN,ELECTROLYTIC SEPARATION OPELECTROLYSIS OP OXIDES OP
NOB I LI FIRSTELECTRO-DEPOSITSPEROX IDEOPLEANOMENCLATURENORWEGIUM, SEPARATION OP
COBALTLEADMANGANESEPALLAD IUMS ILVERHYDROGEN
,ELECTROLYSIS OP
PERSULPHURIC ACID , SEPARATION OPPHOSPATE OP SOD IUM , ELECTROLYSIS OPPHOSPHORIC AC ID , ELECTROLYSIS OPPHOSPHORUS
,ELECTROLYTIC SEPARATION OPCHLORIDE
, BROM IDE , AND IODIDE 0PHYSICAL STATES OP ELECTRO DEPOSITSPLATIN IC CHLORIDE , ELECTROLYSIS OPPLATINUM
,SEPARATION OPFLUORIDE
,ELECTROLYTIC FORMAT IO
INDEX.
PLUMB IC FLUORIDE, ELECTROLYSIS OPN ITRATE,
PEROXIDE
POLARISATION OP ELECTRODES .POTASSIUM, SEPARATION OPANTIMON IATE, ELECTROLYSIS OP
CARBONATECHLORATECHLORIDECYAN IDEFERRICYAN IDEFERROCYAN IDEFLUORIDEHYDRATEIOD IDEN ITRATEPLUMBATE
POTENTIALPREPARING SOLUTIONS POR ELECTROLYSIS .PRESSURE , EPPECT OP, UPON ELECTROLYSIS OP
PROCESS , S IMPLE IMMERS ION .SINGLE
PURIPICAT ION OP COPPER BY ELECTROLYSIS .
PURITY OP ELECTRO-DEPOSITED METALSQUANTITY OP 28
FROM D IPPERENT METALS 29
REPINING COPPER BY ELECTROLYSISRELATIONS OP ELECTRO-CHEM ICALS TO ORDINARYCHEM ICAL ACTION .
RES ISTANCERHOD IUM , SEPARATION OP ..
RITTER PIRST DEPOS ITS PEROXIDE OPRUBID IUM , SEPARATION OPRUTHENIUMSECONDARY EPPECTS OP ELECTROLYSIS . .SELENATE OP N ICKEL , ELECTROLYS IS OPSELENIUM , ELECTROLYTIC SEPARATION OPSELP-DEPOS ITION OP METALSSEPARATE CURRENT PROCESSSEPARATION OP FLUORINESILICIC ANHYDRIDE, SEPARATION OP, BY ELECTROLYS IS 49S ILICON, SEPARATION OP , BY ELECTROLYSIS 4 8-49S ILVER, SEPARATION OP
FIRST COATED WITH COPPER BY ELECTROPERCHLORATE, ELECTROLYSIS OP . 74PEROX IDE, ELECTROLYTIC FORMATION OP 2 70
S IMPLE IMMERS ION PROCESSS INGLE CELL PROCESSSOD IUM , SEPARATION OP
BORATE , ELECTROLYS IS OPCARBONATESCHLORIDEFLUORIDEPHOSPHATESULPHATETUNGSTATE
SOLUTIONS , How PREPARED POR ELECTROLYSIS”SOUNDS EM ITTED DURING ELECTROIYSIs
0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0
SOURCE OP VOLTA IC CURRE NTSTANN IC CHLORIDESTANNOUS ELECTROLYSIS OP
FLUORIDESTRENGTH OP CURRENTSTRONTIUM , SEPARATION OPSULPHATE OP AMMON IUM , ELECTROLYS IS OP
CERIUMCOBALTCOPPERGALLIUMIRONMANGANESEN ICKELS I LVER
0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 .
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
TEMPERATURE : ITS INPLUENCE ON ELECTROLYS ISTELLURIUM , SEPARATION OP
CHLORIDE,ELECTROLYSIS OP .
FLUORIDE 0 0 0 0 -0 0 0
TERBROMIDE OP ANTIMONY, ELECTROLYSIS OPTERCHLORIDE OP0 0
0 0
0 0
0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0 0
0 0 0 0 0 0
COMPOUNDS , ELECTROLYTIC ANALYSIS OP .CHLORIDE , ELECTROLYSIS OPBIFLUORIDECRYSTALS FORMED BY ELECTROLYSIS
TIN AND COPPER ALLOYS,SEPARATION OPTITAN IUM , SEPARATION OPTRANSPORT OP IONSTUNGSTATE OP SOD IUM , ELECTROLYS IS OPTUNGSTEN , SEPARATION OP
UNIT OF CONDUCT ION ' RESM ANCE o a o 0 o o o 0 o 0 o o 0 0
ELECTROMOTIVE FORCEDENSITY OP CURRENTQUANTITYSTRENGTH
URAN IUM , ELECTRO-DEPOSITION OPCOMPOUNDS,ELECTROLYTIC ANAL. OP
SOLUTIONS, ELECTROLYSIS OP 9
VANAD IUM , SEPARATION OPCOMPOUNDS , ELM TROLY
‘
I‘
IC ANAL. OPVOLTA ’S GREAT D ISCOVERYVOLTAIC ACTION , THEORY OP
AND ELECTROLYTIC ACTION , INTIMATECONNECT ION BETWEENAND ELECTROLYTICACTION ,D ISTINCTION
0 0 0 0 0 0
SOURCE OPMODES OP GENERATIONSERIES .
WATER , ELECTROLYSIS OPWOLLASTON FIRST DEPOSITS COPPER UPON S I LVERZINC
,SEPARATION OP 2
COMPOUNDS, ELECTROLYTIC ANALYS IS OPSELP-DEPOS ITION OPCHLORIDE , ELECTROLYS IS OPPOTASS IC CYAN IDESULPHATEANDCOPPERALLOYS,ELECTRO-DEPOSI TIONOPCOPPER AND N ICKEL
ZIRCON IUMZOSIMUS’S EARLY EXPERIMENTS
SULPHATE OP SODIUM,ELECTROLYSIS OPTHALLIUM ,
ZINCSULPH IDE, HYDRIC, ELECTROLYTIC FORMATION OPSULPH IDES OP ARSEN IC
,ANTIMONY
,AND T IN ,
ELECTROLYSIS OPSULPHUR D IOX IDE , ELECTROLYSIS OP
ELECTROLYTIC SEPARATION OPSULPHURIC AC ID , ELECTROLYSIS OPSULPHUROUS ANHYDRIDESULZ ER’S EXPERIMENTS
MARSEN ICGOLD
TERIOD IDE OP ANTIMONYTERMS EMPLOYED IN ELECTRO-CHEM ISTRYTERoxIDE OP ANTIMONY
,ELECTROLYS IS OPTERSULPH IDE OPTETRACHLORIDE OP TIN
PLATINUM,ELECTROLYS IS OP
THALLIUM , SEPARATION OPCOMPOUNDS, ELECTROLYT IC ANAL. OPSULPHATE
,ELECTROLYS IS OP .
THEOR IES OP ELECTROLYS ISTHEORY OP VOLTAIC ACTIONTHORIUM , SEPARATION OPTIN
INTRODUCTION.
No separate treatise on Electro-Chemistry exists in the
English language. The facts relating to the subject lie
scattered in a great number oi_
books and periodicals.
Perceiving the utility of such a treatise,I have collected
the numerous truths yet discovered in the subject and
arranged them in consecutive order in the following pages.
The treatise is not, however, merely a systematic and
orderly collection of facts,but contains also brief descriptions
of the known laws and general truths which underlie them.
The scope of the treatise is limited to the Electro
Chemistry of what is conventionally termed mineral com
pounds. Whilst nearly all the ordinary liquid and liquefiable
salts belonging to inorganic chemistry have been subjected
to the action of an electric current,and the effects observed ,
the influence of the current upon organic substances,
although a subject of great extent, has hitherto been com
paratively little investigated, and the facts as yet obtained
in organic electrolysis are of an isolated and fragmentary
character.
As the purpose for which the matter of this book was
originally written rendered it advisable to limit the scope
INTRODUCTI ON.
of the subject and to compress a large amount of informa
tion into a small compass, the laws and principles of the
subject are only briefly illustrated.
The present treatise is essentially a Scientific one, and all
facts and information of a purely Technical character have
been purposely omitted.
G. GORE.
Birmingham,1885.
ELECTED-CHEMISTRY.
INORGANIC.
THE present series of articles is intended to contain , in systematic order
,the chief principles and facts of electro—chemistry,
and to supply to the student of electro-plating or electro-metallurgy a scientific basis upon which to build the additional practical knowledge and experience of his trade. As the series isa purely scientific one , i t will not include such technical detailsor particulars as will enable the practical worker to obtain
perfect workshop results ; these may be obtained from techn ical books on electro-metallurgy, combined with actual workshop experience. A scientific foundation
, such as is here given ,of the art of electro-metallurgy, is, however, indispensable tothe electro~depositor who wishes to excel in his calling, andshould be studied previously to and simultaneously with practical working. It is partly in consequence of deficiency ofsuch fundamental knowledge by the British workman (and
p artly to the undue pursuit of weal th by his employers) thatEnglish manufactures are gradually being transferred to foreignlands. Whilst
,also
,the series of articles will contain the chief
facts upon which the comparatively new art of electro-chem ical analysis of minerals and alloys is based
,it will not supply
t he technical details necessary for the accurate quantitatived etermination of metals by electro-chemical processes references to sources of such information will
,however
,be given.
The molecular weights of substances,as given at the heads
of the paragraphs,are in n early all cases those of the anhy
d rous ones for those of the hydrated compounds the studentis referred to books on chemistry.
History — The history of electro-chemistry requires only abrief d escription. Ages before the discovery of voltaic electricity i t was known that various metals, by being simply immersed in metallic solutions
,became coated with the metal
previously dissolved in the liquid. Thousands of years agoZ osimus mentioned the deposition of bright metallic co pperupon iron immersed in a solution of a salt of copper. In they ear 1 752Sulzer remarked,
“ If you join two pieces of leadand silver
,so that they shall be upon the same plane, and
then lay them upon the tongue, you will notice a certain
B
taste resembling that of green vi triol,while each piece apart
produces no such sensation.”Paetz and Van Troostvik also,
in the year 17 90, decomposed water by passing electric sparksthrough it by means of very fine gold wires.It was, however, the discovery by Volta, in 1799 , of his
electric battery which gave the first great impulse to electrochemistry. By means of it Nicholson and Carlisle first decomposed water by means of a voltaic current from a battery onMay 2nd
,1 800 and soon afterwards Dr. Henry
,of Man
chester,decomposed nitri c and sulphuric acids
,and also
ammonia by similar means. During the next year Dr.Wollaston discovered that if a piece of silver in connectionwith a more positive metal be put into a solution of copper ~
the silver becomes coated with copper,which coating will
stand the Operation of burnishing. In the year 1801 Gerboinalso first noticed the movements produced in mercury duringthe act of electrolysis. In 1 803 E isinger and Berzelius discovered that by means of a voltaic current the elements of
water and of neutral salts were transferred to the respectivepolar wires immersed in the liquid ; and Cruickshank, about
‘
the same time, observed the electro-deposition of lead , copper,and silver upon one of the polar wires (the one connectedwith the zinc end of the battery) immersed in solutions ofsalts of those metals, and was thus led to suggest the analysisof
'
minerals by means of the voltaic current. In 1805 Bru
g natelli observed the electro-deposition of gold upon silverwhen the former was made the negative ole in a solution ofa
inmoniuret of gold he also discovered the electrod epositiono z mc.
The most striking proof, however, of the great chemicalpower of the electri c current was the discovery
,on October
the 6th,1 807 , by Sir Humphrey Davy, of the electrolytic
decomposition of potash and soda, and the liberation of theirrespective metals
,by a current from a voltaic battery com
posed of 274 cells. In 1826 Nobili discovered the depo sitionof peroxide of lead in films of beautiful colour upon the
platinum p late which conveyed a voltaic current into a
solution of acetate of lead , and Ritter subsequently discovered the deposition of peroxide of si lver from a solutionof argentic nitrate under similar conditions. In 1834 Faradaydiscovered the important truth that, by the passage of anelectric current through an undivided series of solutions ofvarious metallic salts
,or through those salts whilst in a
state of fusion, the quantity of each salt decomposed was indirect
proportion to the amount of current. Also that the
q uantities of the different metals dissolved or deposited werein definite proportions by weight, and that those proportionswere identical with those of the ordinary chemical equivalentsof thosemetals ; and he thus established the law of definite
:
( 3 )
electro chemical action. And in 1837 Dr. Golding Bird suc
ceeded in decomposing, by means of feeble voltaic currents,solutions of the chlorides of sodium and potassium
,and
depositing their respective metals into mercury.As the subject of electro-chemistry is a very larg e one, i t
is only briefly treated in the following series of articles. Thegeneral principles and phenomena will be first explained
,and
then will follow an account of the action of the current uponindividual substances.
Defi nition of Electro-Chemical Action .— Electro-chemicalaction is chemical change produced by means of an electriccurrent, and usually consists of the decomposition of a com
pound liquid,the liquid being resolved into its constituent
parts in certain definite proportions by weight it is alsooften attended by chemical union of a metal, in certain definiteproportions by weight
,with one of the elements of the liquid.
It is usually limited to combinations of conducting substancesonly.
Chief Cond itions of Electro-Ch emical Action — The chiefconditions are that the substance must‘
be a liqu id,a compound
body, a conductor of electricity, and traversed by the‘ current.
The liquids decomposable by a current are usuallyof two elementary substances, the one being a metal and theother a non-metal. Liquid alloys, or liquids composed of twonon-metallic elements
,are not usually decomposed. Mixtures
of compounds in solution are commonly decomposed moreeasily than solutions of single compounds 5 for instance, watercontaining sulphuric acid is decomposed much more readily ~
than water alone.Al l the products of electrolysis are set free in an almost .
infinitely thin layer at the immediate surfaces of the conductorsat the parts where the current enters and leaves the liquid.The electro-negative products, such as the non-metallic ,
elements and acids,are either liberated at or combine with
the conductor,by which the current enters the liquid
,and
the electro positive ones, such as metals and alkalies,are
liberated at.
or combine with the conductor by which thecurrent leaves the liquid. The behaviour of individualcombinations of metals and liquids will be subsequentlydescribed.
Conductivity of Liquid s — Liquids present an extremelywide range of conducting power ; whilst some completelyresist the passage of a current from voltaic cells iasingle series
,others transmit freely the current from a single ,
element. Amongst the non-conducting ones may be includedall oils
,benzine
,petrolene
,bisulphide of carbon , the liquid
chlorides of carbon,terchloride and pentachloride of phos
phoras, terchloride of ,arsenic, pentachloride of an timony,
B 2
( 4 )
tetrachloride of tin,zinc-ethyl
,perfectly pure water, bromine,
various liquefied gases, including chlorine, carbonic aubydride, cyanogen, sulphurous anhydride, hydrochloric, hydrobromic
,and hydriodic acids nearly all melted fats and resins
,
fused iodine,sulphur
,phosphorus
,realgar, &c. Amongst the
inferior conductors are aqueous solutions of gum, sugar,
ammonia, boracic acid, mercuric cyanide, and alcoholic solu o
tions of metallic salts ; also melted boracic acid and fusedglass. Amongst the best conducting compound liquids areaqueous solutions of salts of the alkali metals, and of copper,silver and gold, and especially certain fused salts, e.g ., argenticfluoride and chloride.According to H ittorf, the degree of resistance of a liquid toelectrolysis is dependent upon the difficulty with which themolecules exchange their constituents. Those which haveactive chemical properties should therefore conduct the best.Bleekrode contests this view.
Nomenclature.— The electrical decomposition of liquids istermed electrolysis the conductor by which the current is saidto enter the liquid is called the anodc , and the one by whichi t leaves it is termed the cathode. The products into whichthe liquid is decomposed are called ions, those which appearat the anode being anions, and those at the cathode cations.
Non -metals,acids, and peroxides are usually anions, while
metals and alkalies are cations ; electro-negative bodies, therefore
,usually appear at the anode or positive pole
,and electro
positive ones at the cathode or negative pole. The sameelementary substance, however, may appear at the positivepole in one case
,and at the ne ativo pole in another, according
to the circumstance whether t e body it is combined with ismore positive or more negative than itself. For instance
,
iod ine , when combined with a more positive body, such as
hydrogen in hydriodic acid,appears at the an ode ; but when
c ombined with a more negative one, such as oxygen in iodicacid
,i t appears partly at the cathode. Sulphur in suitable
different combinations exhibits the same variation. Hydrogenis almost the only gaseous cation.
Visible Phenomena of Electrolysis. — The phenomenausually seen in a liquid during electrolysis are— at the anode
,
corrosion with or without solution of the anode, gas is evolved,the anode acquires an insoluble coating
,&c. In some liquids
the anode becomes fragile,
‘and falls to powder ; in others itfl ies to pieces
,but this is '
a rare case. Silver in dilute hydrofluoric acid is an example of the former, and wood charcoal inanhydrous hydrofluoric acid is an instance of the latter. Atthe cathode, a soluble substance is set free and dissolves, or a
gas, a. liquid, or a solid is liberated, and is either absorbed byt he c athode, or adheres to it, or is d issolved by the liquid, or
( 5 )
escapes. The layers of liquid also in contact with theelectrodes frequently alter in specific gravi ty
,that at the
anod e usually becomes heavier, and descends, and that at thecathode lighter
,and ascends.
Faraday, by passing an electric current upwards through astrong solution of “ Epsom salt”into a layer of distilledwater lying upon it, observed that a layer of magnesia formedat the upper surface of the lower liquid where i t touched thewater, as if the water acted as a cathode. Dan iell also sub
sequently passed an upward current of electricity throughsolutions of the nitrates of silver
,mercury, and lead, and of
the sulphates of palladium,copper, iron, and magnesium,
into a dilute one of caustic potash , separated from them bya thin horizontal diaphragm of bladder. Oxygen was determined to the upper
,and the respective metals to the lower
surface of the diaphragm,and coatings of metal
,more or less
oxidised , were formed against the latter surface, the oxidationbeing more complete the more oxidable the metal ; with themagnesic solution a coating of oxide alone was formed. Morerecently (seeProceedings of the Royal Society, Nos. 212, p. 84,and 217 , 1 88 1 , p. 142) I have stated , and shown by suitableexperiments
,that “ every inequality of composition or of ,
internal structure of the liquid in the path of the currentmust act to some extent as an electrode,
”and have also shownthat a variety of phenomena take place at such a surface of”
mutual contact of two liquids when an electric current passes .
through it.
Movements of Liquid Electrodes — As early as the year1801 Gerboin observed the peculiar twitching movements ofmercury whilst undergoing electrolysis, and which are now
known to be due to electro-chemical action,and subsequently
Sir H .Davy, Sir J. Herschel, and others investigated them.
These movements are due to the formation and destruction,attended by contraction and expansion , of films upon themercury, and would probably occur with other metallic electrodes whilst in the liquid state in suitable liquids. (SeaGmelin’s “ Handbook of Chemistry,
”Vol. I., pp. 38 1Sound s Emitted during Electrolysis — Whilst investig atw
ing these peculiar movements and the thermic changes of
electrolysis I discovered that in certain liquids a humming ,
sound is emitted by electrodes of mercury, and that the sur
face of the mercury is covered with minute waves during thepassage of the current. I also found that the current wasintermittent during these vibrations (see Proceedings of theRoyal Society, Sounds are not unfrequently emittedalso from other metals whilst depositing, e.y. from antimony.These are sometimes produced by contraction and cracking Ofthe metals, at other times by explosion of bubbles of gas.
Decomposability of Electrolytes — The degrees of facilitywith which different electrolytes are
‘
decomposed are different.Faraday has given the following order, the first named beingthe easiest —Solution of potassic iodide, fused chloride ofs ilver
,of zinc, of lead, melted iodide of lead, hydrochloric
acid,dilute sulphuric acid. Smee gives nitric acid
,solution
of chloride of gold, nitrate of palladium,chloride of platinum,
argentic n itrate,cupric sulphate
,stannic sulphate
,dilute
sulphuric acid , solutions of the sulphates of cadmium,zinc
,
nickel,iron
,and magnesium, and those of salts of the alkalies
generally. D ilute sulphuric acid offers less resistance to electrolysis than one of zinc sulphate
,and more than one of
cupric sulphate (Favre, Comptes Rendus, Vol. LXXIII. Journal
of theChemical Society, 2nd series, Vol. X.,p. I have re
peatedly observed that hydrochloric acid is decomposed morereadily than water, and water more easily than hydrofluoricacid
,also a solution of selenic acid before one of selenate of
nickel. The readiness of decomposability of an electrolytedepends upon several conditions, and especially upon then ature of the electrodes ; thus a solution of potassic cyanideis readily decomposed when the anode is composed of pallad ium
,silver
,or copper
,but with diffi culty when it is formed
'of iron or platinum. A large field of research exists in this
,part of the subject.The decomposability of a liquid is usually increased by rise
-Oi temperature ; i t is also influenced by the length of thet liquid portion of the circuit, which is the part in which thegreatest resistan ce exists to the passage of the current. Thishas been shown by Gladstone and Tribe
,who decomposed
water by immersing in it a pure zinc plate previously coatedelectrolytically with a loose deposit of spongy copper or plat inum
,when two plates of those metals connected together
a nd Immersed at a distance from each other in the liquidwould not decompose it, and have thus shown that the dis:sociation of a binary compound may take place at infinitesim ally short distances
,when it would not take place where the
layer of liquid is enough to offer resistance to the current”(Proceedings of theRoyal Society, Vol. XX.
, p.According to Helmholtz
,electrolysis of water by a voltaic
current is possible only when the chemical processes in thebattery
,taken together
,can produce more heat than the
oxygen and hydrogen generated in the voltameter,and
therefore that about l ‘
Ll Daniell cells are required for a continuous decomposition of water. A single Daniell connectedwi th platinum electrodes in dilute sulphuri c acid producesonly polarisation
,no visible decomposition
,the voltameter
acting as a condenser of immense capacity (JournalChemical Society, 2nd series
,Vol. XL ,
p. As a matter offact; however, a feeble current passes it the water in the
voltameter contains dissolved oxygen,or the platinum plates
o ccluded hydrogen.According to D. Tommasi , in order that decomposition
may take place when a current passes through several electrolytes, it is necessary that the quantity of heat should beequal to the sum of the quantities absorbed by each electrolyte, plus the quantity necessary to overcome the totalresistance of the electrolytes. By heat produced by thebattery is meant that transmissible to the circuit. In manyc ases in which there is no decomposition when both electrodes are of platinum
,decomposition takes place when the
anode consists of some oxidable metal, such as copper or tin.”
“ Of two compounds,that one is decomposed by preference
which requires the least thermic energy”(Journal of the
C hemical Society, Vol. XLII., 1882, pp. 134, 353, 7 89,and see also Favre
,
“Watt’s D ictionary ofChemistry,
”Vol. VII., .pOn the subject of “ The Limits of Electrolysis consult
Berthelot (Journal of the C hemical Society, Vol. XLII., 1882,pp. 260andAccording to E. Obach
,liquid mixtures of metals do nOt
,snfler electrolysis. His experiments were made with alloys ofsodium and mercury
,of sodium and potassium
,and of tin with
lead. ,The portions of alloy around the poles after passage ofthe current were unaltered in chemical composition (Journal ofthe Chemical Society, 1876, Part IL , p. 37 Chemisches Central
Blatt,18 75 , p.
Conduction in Electrolytes with out Decomposition.Whether this takes place or not is an important question, anda fter many researches on the subject electricians are even nownot unanimous respecting it. According to Favre
’s experi
ments (Comp tes Rendus Academic des Sciences, Vol. LXXIIIAp. true conductionwithout electrolysis does occur whentwo Smee cells are used to electrolyse dilute sulphuric acid. Inthe electrolysis of fused argentic fluoride, also with sheet silverelectrodes
,I observed that the liquid conducted the current
'
with a most extraordinary degree of facility apparently out ofall proportion to the weight of metal deposited. ConclusiVe
experimental evidence 18,however
,still much required to settle
the question. With a current of insufficient electromotiveforce to decompose an electrolyte
,either the electric charges
must accumulate on the electrodes, and the liquid act as'
a
d ielectric,or they must be transm itted by convection or con
d uction.
Circumstances which Aff ect th e Kind of Deposit. —Boththe chemical composition and the physical quality of thesubstances set free at the electrodes are aflected by variousc ircumstances by the composition of the liquid and its degree
( 8 )
of fluidity by the strength of the current by its density,or
strength in relation to amount of surface of the electrode bytemperature, &c., and by various other circumstances.The products of electrolysis vary also according to the kind
of electrolytic arrangement employed. In the simple immersion one they are mixed with those of voltaic action. Inthe case of two metals in two liquids separated by a porousdivision, the products of voltaic action and electrolysis are
largely kept separate,and in the case of electrolysis in an
undivided cell by means of a separate current, the anode and
cathod e products become mixed .
The composition of the liquid is a fundamental condition ,and variation of it has usually very powerful effects. Theaddition of an extra ingredient may cause entirely differentsubstances to appear at each of the electrodes
,or alter both
the quantity and physical condition of the deposits. Analteration of the degree of fluidity acts similarly
,but less
powerfully. Wh ilst also with one strength or degree ofdensity of current a single substan ce only may appear at eachelectrode, with a current of greater streng th or densityadditional bodies not unfrequently are liberated . By eitherdecreasing thepreportion of watermixed with potassic hydrate,or increasing the strength or degree of densi ty of the current,instead of oxygen and hydrogen alone being evolved,potassium is also set free. Aweak current passing throughan ordinary silver-plating liquid containing much free potassiccyanide deposits hydrogen only but by increasing the densi tyof the current silver is also liberated. It was by obeyingthese conditions that Davy isolated potassium
,and Bunsen
deposi ted chromium. Other investigators also succeeded inobtaining highly oxidable metals in the form of amalgams
,
without the use of powerful currents , by employing as a
cathod e mercury,which absorbed the deposits, and thus largely
prevented them from redissolving.The density of the current affects also the physical preper
ties of deposited metals. With aweak current and slow actionmetals are not unfrequently deposited in a crystalline state,whilst with a strong one they are thrown down as a soft blackpowder. A nearly saturated solution of cupric sulphate,acidulated with dilute sulphuric acid to a suitable extent,yields ductile metal when the rate of deposition is about halfan ounce of metal per square foot of cathode surface per hour.The degree of density of the current not only affects thephysical properties of cations, but also those of anions in somecases. Thus a stronger current is usually required to liberateozon e than to set free ordinary oxygen.Every different metallic solution
,and at every different
temperature,must be electrolysed at a particular rate in order
to obtain from i t metal in the state of crystals, reguline metal,
( 10 )
equal in value to that done by it at any other of the sameseries in the same time. In the decomposition of water
,there
fore,by an electric current we obtain two parts by weight of
hydrogen for each 16 parts by weight of oxygen,and in con
sequence of the specific gravity of the latter g as being sixteentimes g reater than that of the former, the relative volumes ofthem are as two to one. This exact relation of the quantity ofthe current to the amount of its chemical eflect with differentsubstances is known as the law of definite electro-chemicalaction
,and was discovered by Faraday,
lVith nearly all, if not all electrolytes, Faraday’
s law ofd efinite electro-chemical action is supposed to be true for eventhe very smallest currents. The true electro-chemical equivalent of a sing le substance, however, is only obtained in certaincases. In some instances a portion of the current passesthroug h another ingredient of the liquid , and two substan cesare deposited simultaneously
,and form the equivalent. The
alteration of weight of either electrode during electrolysis isoften not a true measure of current
,because the metal is
l iable to ordinary chemical action. The true measure is thetotal amount of substances liberated
,taken before they have
had time to suffer ordinary chemical change .
Influence of Temperature , &e., on Electrolysis — Changeof temperature has a great effect. Both the elec tric conduetivity and the diffusive power of saline solutions increase byrise of temperature , and each of these circumstances greatlypromotes electrolysis. Rise of temperature affects also therelative proportions of current conveyed by the d ifferent in
g redien ts of a mixed electrolyte ; for instance, I found thatin the electrolysis of an acidified solution of cupric sulphatewith copper electrodes a considerable deficiency of depositedcopper
,sometimes amounting to as much as 16 per cent ,
mayresult through employing a
b
hot solution. (“ Electrolysis of
Sulphate of Copper,”Proceed ings of the Birm ingham Philo
sozohical Society, Vol. III. p. 7 5 ; The E lectrician , Vol. VIII.pp. 27 1 Very few experiments have as yet been madeon the influence of great pressure (see Section 48) or ofmagnetism on electrolysis. Remsen , however, found bydepositing copper from a solution of cupric sulphate containedin a thin vessel of sheet iron
,placed upon the pole of a
powerful permanent magnet,that the deposi t occurred in a
fairly uniform way on the ,
entire surface of the iron exceptat the parts marking the outlines of the poles. These lineswere strongly marked as depressions in the copper. Theaction was still more striking when an electro magnet wasused instead of the permanent one. In a narrow space marking the outline of the pole there was no deposit, Withinthis line it was fairly uniform,
but outside of it the copper
( 1 1 )
aggregated in irregular ridges, running at right angles to thelines of force, and
t )
apparently coinciding with those markingthe equipotential surfaces.
Relations of Electro-Ch emical to Ord inary Ch emicalAction. -E lectrolytic changes obey the same law of equivalence of action as ordinary chemical ones
,and electro chemical
action by a separate current may be viewed as Ordinai ychemical action taking place in one large and measurablec ircuit instead of in a multitude of excessively small and non
measurable ones and conversely, ordinary chemical corrosionof metals in electrolytes may be viewed as electro-chemicalaction taking place in an infinite number of such minutecircuits.The electrolytic c ircuits in which electric currents flow
may be of any degree of magnitude , from these small onesupwards, and such currents, of various degrees of magnitude,may circulate simultaneously in the same metals and liquid .
Electro chemical action,therefore
,does not necessarily exclude
ordinary chemical change. One large current may flowthrough the electrodes
0
and liquid of an electrolytic cell,
whilst “ local action (i. ,e. ordinary chemical action in patches)
in lesser circuits is taking place upon each of th e electrodes,
and also whilst ordinary chemical action is occurring uniformlyupon them.
When an electric current is passed through an electrolyte,
whether attended by corrosion of the anode or deposition ofmetal upon the cathode or not, the layers of liquid in contactwith each electrode become changed in chemical compositionand density
,and are thus indirectly set in motion by the
influence of the current, and in consequence of this the ordin ary chemical action upon them is altered. In some casesalkal i collects around the cathode, and acid around the anodein others the liquid around the former becomes more diluteand ascends
,whilst that around the latter becomes more satu
rated with salt and descends. In others, again, insoluble g asis evolved from each electrode, and causes an upward motionof l iquid
,and in others the gas d issolves in the liquid and
alters its degree of corrosive power, as well as of specificg ravity and in some of these cases, by in c1 easing the density oft he current up to a certain point the ordinary chemical actionof the liquid upon the cathode is diminished until all suchcorrosion ceases. This point I have termed the electrolyticbalance of chemical corrosion, and have investigated it in thecase of silver in an ordinary cyanide plating solution (see Proceedings of the Birmingham Philosophical Society, Vol. III., .pp268— 305
,also an abstract in TheE lectrician, Vol. X . p.
Many other cases in which ordinary chemical corrosion isbalanced and prevented by electro chemical action remain to
be investigated . In some cases the rate of corrosion of acathod e is increased during electrolysis, in consequence of theevolution of hydrogen and consequent motion of the liquidbringing fresh COIrosive particles into contact with it (see“ Corrosion of Cathodes,
”Proceedings of theBirminghamPhiloso
phical Society, Vol. III., p. 305 The E lectrician,Vol. XL ,
p. 213}
Electrolytic Balance of Ch emical Corrosion . Any mixedelectrolyte with a current passing through it and setting freeone only of its constituents at a corrodible cathode, and thecurrent then gradually increased until a second cation constituen t just begins to be deposi ted, constitutes an exampleof “ electrolytic balance. Such a case is that of an acidifiedsolution of cupric sulphate, wi th copper electrodes, with thecurrent increased until metal begins to be deposited or thatof the ordinary cyanide of silver plating solution containingmuch free potassic cyanide with electrodes of silver, similarlytreated.Such a silver solution, sufi
'
ering electrolysis at its“ balance
point,
”forms an excellent illustration of the compensationand balance of a number of molecular forces
,the alteration of
any one of which disturbs the remaining ones. Even a
change of temperature may be included in this statement. Itis a case of balance of powers in which the state of equipoised epends upon the united and simultaneous action of at leastseven or eight different influences
,viz.
,ordinary chemical
corrosion,strength of current
,nature of cathode
,size of
cathode,temperature
,proportions of water, of argento-potassic
cyanide,free potassic cyanide
,and of the soluble salts, &c.,
present in the form of impurities. Additional causes, or
conditions,might also be introduced
,which by their pre
sence would probably affect the state of balance, such, forinstance, as by dissolving in the liquid various salts or othersubstances.Several of these causes or conditions may be mod ified so
as to alter the balance either in one or the opposite manner.Thus
,increased chemical corrosive power, a larger cathode,
more free potassic cyanide,less argentic cyanide, or less
strength of current alter the balance in one d irection, whilsttheir opposites alter it in the contrary one.Such experiments also show that the various conditions of
the state of balance may either assist or counteract eachother ; that an in crease of current is equivalent to a decreaseof argentic cyan ide
,i f the one is increased the other must
be decreased in order to maintain the state of the balancethat an addition to the amount of free potassic cyanide,by diminishing resistance, is equivalent to an increase ofi
current ; that a decrease of cathode surface necessitates
( 1 3 )
either a decrease of argentic cyanide or of current ; that arise of temperature is balanced by an increase of current
,
and so on.All these influences have numerical values. In the experi
ments referred to it is shown that a rise of temperature of theliquid of 60Fahrenheit degrees
,i.e., from 60
°
to 120° F.,is
balanced by an increased strength of current from 002306 to003282
,or 000976 ampere.
The arrangement and use of a depositing solution in such amanner constitutes a method of detecting the molecularinfluences of substances dissolved in electrolytes, and of determining to a certain extent their kind and amount of influencesby their effect and degree of power in altering the“ balancepoint”either in one direction or the opposite. It was foundthat the mere presence and admixture in solution of even asmall quantity of argento-potassic cyanide in the above liquidaltered the molecular arrangement of the free potassic cyanidein such a way as to diminish its power of alone transmittingthe current into a silver cathode
,and increased the tendency
of the current to pass into the cathode partly by means of thedouble salt.The phenomena of the “ balance point constitute also an
interesting.example of molecular equilibrium,
in which thebalance point may be compared to a ball suspended by anelastic cord and having attached to it a number of othersimilar cords in a state of tension
,each drawing it in a different
direction. In such a case an alteration of the degree of strainof any one of the cords changes that of all the others, andalters the position of the ball.
Secondary Effects of Electrolysis — III very many casesthe new substances actually observed at the electrodes arenot those set free by the current, but are products or resultsof the action of those substances upon the liquid or upon theelectrod es. Thus
,when potassium is deposited from a solu
tion of one of its salts into a cathode of mercury, the liquidin contact with the mercury becomes alkaline ; when iodine isset free from the cathode in a solution of iodic acid, it is dueto the deoxidising action upon the iodic acid of the hydrogenliberated there by the electrolysis of the water or of the iodicacid , and when it is set free at the anode during electrolysis ofa solution of hydriodic acid it may be viewed as a direct resultof the current or as a secondary result of liberated oxygen.The peroxide of si lver formed at an anode of platinum in asolution of argentic nitrate may be viewed as a secondary product due to the action of the liberated oxygen or ozone uponthe silver of the liquid. In many cases it is difficult to determine whether a liberated substance is due to primary or tosecondary action.
Faraday advanced the view that only these compounds ofthe first order are directly decomposable by the electric currentwhich contain one atom of one of their elements for each atomof the other for instance, compounds containing one atom ofhydrogen or metal with one atom of oxygen , iodine, bromine,chlorine
,fluorine
,or cyanogen , whilst borac ic anhydride
sulphurous anhydride (S02), sulphuric anhydride (SO iodid eof sulphur, the chlorides of phosphorus (P013 andchloride of sulphur (SQCI), chloride of carbon (C tetrachloride oi tin (SmCl4l, terchloride of arsenic pentachloride oi antimony (SbClb), are non-conductors of electricity,and incapable of electrolysis.”I have observed that thedecomposability of a salt depends upon the kind of liquid inwhich it is dissolved e.g ., the iodide and bromide of antimony,both of which conduct and are decomposed when dissolved inacidulated water
,do not conduct and are not decomposed
when dissolved in carbonic bisulphide.
Insoluble Coating s on Anod es.— In many cases of electro
lysis of aqueous solutions, the anode does not dissolve, butbecomes coated with an oxide, chloride, fluoride
,cyanide
,
sulphate, or other insoluble salt, usually by chemical union ofthe metal with an ingredient of the liquid. In this way silverin dilute hydrochloric acid becomes coated with argenti cchloride ; in a solution of argento-cyanide of potassium it
becomes covered with argentic cyanide, lead in dilute hydrofluoric acid becomes coated with fluoride
,and so on. In some
cases the insoluble coating occurs not by corrosion of theanode
,but by the oxygen evolved by electrolysis of the water
acting upon the ingredients of the solution ; in this wayvarious peroxides are formed. The formation of peroxidesoccurs upon platinum anodes in solutions of the nitrates ofbismuth, silver, and lead in certain alkaline solutions of lead
,
nickel,and cobalt
,and in those of nitrate and acetate of
manganese,and when the films which are thus formed
are exceed ingly thin their colours are in some cases verymagnificent.
Electrolyt ic Alloys.— In many cases when metals are deposited upon metals, the two substances form alloys ; greyantimony deposi ted upon mercury from a solution of tartaremetic alloys readily, but the black explosive variety doesnot. Tellurium deposited from a solution of its chloride uponplatinum also forms an alloy. Boron
,silicon
,and lithium
,
when deposited from certain fused compounds upon a surfaceof platinum
,also alloy with it. Hydrogen deposited upon
palladium,or upon certain other metals
,iron in particular
,is
absorbed,and imparts to the metal peculiar properties. In
some cases the absorption of the deposited substance continues after deposition has ceased this is only visible in cases
( 15 )
where the deposited coating is extremely thin. A thin filmof deposited copper is absorbed by zinc.
Purity of Electrolytic Deposits — Not only do the deposited substances sometimes alloy with or penetrate intothe mass
,of the cathode, but in some cases during the act of
deposition they combine with some of the elements of theelectrolyte, and are thereby altered in property. In this wayantimony which has been rapidly deposited from a stronglyacidified solution of its oxide in hydrochloric acid containsseveral per cent. of the salt derived from the liquid
,and
possesses the very remarkable property that,if broken
,or
even scratched, it suddenly rises in temperature about sixhundred Fahrenheit degrees ; i t also has the appearance ofhighly burnished steel
,very widely different from the colour
and appearance of the pure grey metal very slowly depositedfrom a feebly acidified solution of tartar emetic in dilutehydrochloric acid. This black antimony gradually loses itslatent heat, explosive power, and brilliant appearance, inthe course of one or two years, the period varying accordingto the thickness of the deposit.It is only in certain cases and in the presence of a collee
tion of suitable fortuitous conditions that a deposited sub
stance is extremely pure ; substances very easily deposited,such as hydrogen and copper
,are usually so chiefly because it
requires a stronger power to deposit most other bodies,also
because in some cases the other easily deposited metals areprecipitated as insoluble salts by ordinary chemical action.Thus lead in an acidified solution of sulphate of copper is precipitated as sulphate similarly silver is precipitated in a solution containing a dissolved chloride. All deposited substancesare
,of course
,more likely to be pure the greater the degree
of purity of the liquid.
Divid ed Electrolysis — When an impure liquid or a mixture of solutions is electrolysed , either a single substancealone may appear at the anode or cathode, or several maybe simultaneously liberated. With a feeble current and largeelectrodes one substance alone may appear at either electrode,but by either increasing the strength of the current ordiminishing the size of the electrodes, a. second , or even a
third substance may be liberated, the current appearing to
divide its action amongst the various compounds present. Theleast electro-positive cation is usually liberated first, and themore positive ones subsequently as the current strength Is In
creased. In all cases weaker affinities appear to be overcomefirst ; but this is only a superficial explanation, the true onebeing much less simple. By employing preportions of thesubstances
,larger as their electro-positive property in the
particular liquid is greater, several may be simultaneously
( 10 )
deposited or themore positive ones may be deposited even inlarger amount than the less positive ones, as for instancepotassium from moist potassic hydrate. It is by obeying theseand other conditions that alloys and mixtures of substancesare usually set free at the electrodes. The order of degree ofelectro-positive state of the metals desired to be deposited mayin most cases be ascertained by connecting the metals in pairswith a galvanometer
,immersing their free ends in the liquid
,
and observing the direction of deflection of the n eedles.In electrolysing a mixture of the sulphates of zinc, cadmium,
and copper,Favre succeeded
,by altering the conditions of the
experiments, in obtaining at will either one, two , or all theth ree metals simultaneously and states that the results of theoperation vary, 1st, with the voltaic energy of the battery ;2nd , with the electrolytic resistance of the salts ; 3rd , withthe relative quantity of each salt and 4th , with the greateror less rapidity of the electrolysis
,which can be regulated.
He concludes that by varying these conditions we are enabledto withdraw from a mixture of salts the different metals insuccession , and thus proposes an electro-chemical analysis(Comptes Rendas, Vol. LXXIII. Journal Chemical Society,2ud series, Vol. X ,
p. This proposal, however, is nota new one.
Polarisation of Electrod es — In consequence of the alteration both of the chem ical composition of the surface of theanode and of that of the cathode, and also of that of thelayer of liquid in contact wi th each of the electrodes by electrolytic action
,the electric state of each of these surfaces is
continually liable to change or,in other words
,the surfaces
become polarised. And as the substances set free at the anod eare usually electro-negative
,and those at the cathode are
usually electro positive,the electric states produced by polari
sation are opposite in kind to the original ones, and tend toproduce an electric current in an Opposite direction to the
p revious one, and therefore weaken that current. Accordingto M‘Gregor (Nature, July 19 , 1883, p. the degree ofpolarisation of electrodes is independent of their degree ofd ifference of potential. By passing an undivided current bymean s of four similar platinum sheet electrodes through twocells containing equal sections but unequal lengths of dilutesulphuric acid (the current being therefore of equal density ineach and the elec trodes of the two vessels of unequal potent ial), he found that the variation by lapse of time of theelectromotive forces of the two cells after cessation of the
p olarising current was similar.
Unequal Electric Action at Electrod es — By the electro~
;lysis of a metallic electrolyte by means of vertical corrodibleelectrodes, the liquid around the anode usually becomes more
( 18 )
deposits the metal in the capillary film. This phenomenon isseen in alkaline liquids as well as in acid ones ; for instance,with silver in a solution of potassic cyanide.The corrosive effect attending this capillary action differs
somewhat with different metals and liquids."
With metallictin
,in particular
,in dilute hydrochloric acid, in some experi
ments of m ine,grooves about °5mm. deep were corroded in its
surface and extended in a vertical direction to a distance ofnearly 7mm. above the level of the liquid. The grooves werecrooked, and had branches like those of a tree, and those uponthe cathod e were longer and deeper than those on a similarsheet of metal in a separate portion of the same liquid notunder electrolysis.
Dep end ence of Electrolysis upon Liquid Diffusion — Thisis a branch of the subject which has hitherto been but littleexamined
,an d much remains to be discovered in it. Many of
the phenomena of electrolysis are,no doubt
,essentially related
to the power of liquid diffusion. An extremely viscous liquidadmits of but slow electrolysis. Long has discovered (Phil.May ,
1880,Vol. IX.
,p. 425 ) that in almost every case the
best conduc ting saline electrolytes are solutions of those saltswhich have the fastest rate of difl
'
usion ,and those are usually
the salts which have the largest molecular volume,and which
also absorb most heat in dissolving. He also arrives at theconclusion that “ the rate of diffusion of a salt is proportionalto the sum of the velocities with which its component atoms
' move during electrolysis.”Electrolytic Diffusion of Liquids — I have experimentally
investigated this converse part of the subject (seeProceedingsof Royal Society, No. 203, 1880, p. 322, and No. 212, 1881 ,pp. 56 and have shown that an electric current willcause a liquid to d ifl
'
use, and I discovered that when such acurrent was passed up or down through the surfaces of mutualcontac t of certain aqueous solutions of different specific
g ravities lying upon each other in welld efined layers, thebounding surfaces of contact of the two liquids became indefin ite where the current passed downwards from the lighter tofthe heavier solution, and became more sharply defined whereit passed upwards from the heavier into the lighter one andithat, on reversing the current several times in succession , aftersu itable intervals of time
,these effects were reversed with
each such change of direction also,in various cases in which
the contiguous boundary films of the two liquids had becomemixed, and the line of separation indefinite , the liquids separated by the influence of the upward electric current
,and the
line of separation became as perfect as that between strata ofoil and water lying upon each other. I also observed, let, theproduction of definite lines, not only where the current passed
( 19 )
from the heavier into the lighter solution, but also (in cer taincases) at the surface where it passed from the lighter to theheavier one. 2nd. The production in some cases of two orthree separate lines at the former situation, and less frequently
i also at the latter one. And , 3rd, an apparent movement ofthe mass of the heavier solution, usually In the direction ofthe electric current, but in certain exceptional cases in thereverse direction. By further experiment (see Proceedings oftheRoyal Society, I ascertained that
, let,in certain cases the upper and lighter liquid difl
'
used downwards continuously through the meniscus, or surface of separation of the two liquids, during the passage of an upwardelectric current ; and, 2nd , that during the continuance of thecurrent either no manifest expansion of the upper liquidoccurred, and that equal volumes of liquid diffused in twoopposite directions through the meniscus, or that any expansion of the upper liquid was compensated by downwardd iffusion of an equal bulk of that liquid ; or that the unitedvolumes of metal deposited from the upper liquid, and of theacid element from which it had been separated by electrolysis,were greater than before such separation
,and that this was
c ompensated by the volume of liquid diffused downwardsthrough the meniscus. In these latter experiments themeniscus retained its position during the passage of thecurrent, thereby proving that the actual bulk of the upperliquid remained the same whilst diffusion of a portion of thatliquid took place downwards through the meniscus.
Transport of Ions.— Hittorf and G.Wiedemann found thatusually the velocity of transport in electrolysis of anion andcation are different
,and F. Kohlrausch discovered that in
dilute solutions of salts,acids, and alkalies every ion under
the influence of currents of equal density moves wi th its own
particular velocity, independently of others moving at thesame time in the same or Opposite direction. The order ofvelocity of cations
,the first named being the fastest
,was
hydrogen,potassium, ammonium,
silver, sodium,barium
,
copper,strontium
,calcium
,magnesium
,zinc
,lithium
,and
of anions was hydroxyl,iodine
,bromine
,cyanogen
,chlorine
,
NO3,010 and the halogen of acetic acid.
Relations of Electrolysis to Heat — In consequence ofchemical action and of the passage of an electric currentfrom one substance to another
,changes of temperature occur
at each electrode,and
’
at each junction of two differentliquids. These changes are different in every different case,and have been but little investigated. With an anode ofcopper in an acidulated solution of its sulphate, heat isevolved by the oxidation of the metal ; but with one of
, platinum i n dilute sulphuric acid, heat is absorbed, ando 2
( 20 )
oxygen is reduced to the elementa ry state. At the cathode,in the former liquid
,copper is liberated and heat absorbed ;
but with a platinum cathode in nitri c acid,heat is set free by
oxidation of the deposited hydrogen.According to Favre (Comp tes Rendas, Vol. LXXIII., pp
l , l 86 although in certain cases themetal dissolved at the anod e is all reproduced at the cathod e,heat is liberated which is not transmissible to the circuit.The oxides and salts of the alkali “metals
,when subjected to
electrolysis,are decomposed , and give up their metal, which
metal being directly oxidised at the expense of the water, setsfree a quantity of heat which reinforces the voltaic energy ofthe battery. The secondary reactions which accompany electrolysis and produce heat not transmissible to the circuitalways tend to strengthen the energy of the battery whenever the current is weak and when the electrolysis offersgreat resistance. Such secondary reactions are
,for example,
produced by the hydrogen and the oxygen set free duringelectrolysis
,the first being burn ed, the second oxidising any
oxidable substance present (Journal of the Chemical Society,2nd series, Vol. X., pp. 1 10In addition to changes of temperature produced by electrochemical and chemical actions in the electrolyte , heat isevolved by conduction-resistance in the mass of the liquid ;and I have noticed that if two large masses of the same, or oftwo different electrolytes
,are united by an Open short glass
tube of the shape of an hourg lass, and of small diameter.byemploying a suffi ciently strong current the liquid in the
narrow part of the connecting tube may be caused to boil
(“ Influence of Voltaic Currents on Diffusion of Liquids,
”Proceedings of theRoyal Society, 188 1, No. 213, pp. 76Gladstone and Tribe have shown by experiment that if a
strip of metal is immersed at its two ends in a salt of thesame metal in a state of fusion , but of unequal temperatureat the two parts where the metal dips into it, the hotter andof the metal dissolves, and the less heated part receives a
metallic deposit. Copper in fused cupric chloride is anexample (Journal Chemical Society, Vol.XL ,
1881, p.
Th eories of Electro-Ch emical Action — Various theorieshave from time to time been proposed to account for theleading phenomena of electrolysis, but none of them have asyet been very clear or satisfactory. One of the best is thatpropounded by Faraday. He considers that electrolysisresulted from a peculiar corpuscu
’ar action developed in the
direction of the current ; and that it proceeded from a forcewhich was either added to the aflzin ity of the bodies present,or determined the direction of that force. That the electrolyte was a mass of acting
‘
particles, of which all that were in
( 21 )
the course of the current contributed to the teInIinal action,and in consequence of the affinity between the elements beingweakened , or partially neutralised by the current parallel toits own course in one direction
,and strengthened and assisted
in the other,the combined particles acquired a tendency to
move in different directions. The particles of one element,a, cannot travel from one pole to the other, unless they meetwith particles of an opposed substance, b, ready to move inthe opposite direction. For In consequence of their increasedaffinity for these particles
,and the diminution of their affinity
for those which they have left behind, they are continuallyd riven forward.Any tolerably complete theory of electrolysis of a funda
mental character must, however, be a mechanical one, basedupon the assumption of molecular motion, and expressiblein mathematical and geometrical terms. Whilst, also, thetheory must represent the kind of molecular motion whichconstitutes an electric current
,it must also be consistent
with the numerous and varied phenomena attend ing electrochemical action. And as the essential kinds of molecularchange which occur at the electrodes are probably more orless modified in every different case, a complete theory mustadmit of varied application . Clausius considers that the atomsor groups of atoms forming a molecule of an electrolyterevolve around one another
,similarly to planets, and
‘
aresometimes nearer to and sometimes farther from each other
(“Poggendorfi s Annalen,
”CLVI., pp. 6 18 to Favre
s tates (Comptes Rendus, Vol. LXXIII., p. 97 1) that in eachvoltaic couple the molecules are electrolysed successively, andthat when the absolute number of vibrations which correspondto a given intensity of the current have been determined theabsoluteweight of the chemical molecules will be known (JournalChemical Society, 2nd series
,Vol.X.
,p.
The immediate or primary electrolytic chang es are evid ently a result of molecular energy transmitted along thewires from the source of the current ; and the energy so
transmitted is substantially the same in its chief propertiesand electrolytic effects
,whether it proceeds from a voltaic
battery, a thermopile, or a dynamo electric machine. Anytheory, therefore, which explains electrolysis must also bec onsistent with the fact that in the act of electrolysis thehomogeneous electric energy is converted into potential molecular energy as varied In kind as the properties of the liberatede lements. It must also explain why the same element mayin certain cases be an anion in one combination and a cation inanother.
D istinction between Voltaic and Electrolytic Action.These two actions are almost entirely the converse of each
( 22 >
Other the former isa consumer,and the latteraproducer OE
potential molecular energy. In voltaic action substances areburned, in electrolytic they are unburned. In a voltaic cellpotential or stored-up energy of elementary substances is converted into electric current ; in an electrolysis vessel currentis converted into stored-up potential energy in the elementarysubstances liberated at the poles.
Intimate Connection of Voltaic and Electrolytic Action.As in n early every voltaic circuit the current produced at thepositive surface decomposes the liquid at the negative one, andin nearly every electrolytic circuit voltaic currents are pro~duced by difference of chemical composition of the liquids incontact with the two electrod es
,nearly every voltaic circuit is
partly electrolyti c, and nearly every electrolytic circui t ispartly voltaic.According to these views, voltaic action is chemico electric,
‘
and a case of chemical union in all cases ; and true electrolyticaction is always a case of electro-chemical separation, someztimes accompanied by chemical union at the electrodes.The various phenomena of electrolysis are produced not
only by electric currents proceed ing from an extern al source,but also by those produced in the electrolyte itself and alsonot only by currents generated and flowing in circuits ofmeasurable magnitude in that liquid , but also by others incircuits so small that they cannot be measured.In the case of an ordinary voltaic cell or electrolytic
vessel, the positive“and negative surfaces are sufficiently far
asunder to enable us to perceive the action at each ; but inthose of “ local action”and minute circuits, such as thosein cases of dep osition by simple Immersion , or the chemicalsubstitution of one metal for another, as when Iron becomescoated with copper by simply immersing it in a solutionof cupric sulphate, the positive and n egative surfaces ofeach circuit are so excessively small
,so
O
exceedingly neartogether
,and the circuits are so numerous that they cannot be
separately observed , and the entire immersed surface of themetal is covered with inseparable voltaic and electrolytic actions.The substances set free by electrolysis do not always
ap ear ; the instant they are liberated they are subject toor inery chemical action by c ontact with the liquid, the
electrodes, and the atmosphere. Thus,when potassium is
'
s’
et , free at the cathode from a solution of any of its salts, itis instantly oxidised into potash ; or oxygen set free at acopper anode instantly oxidises the copper. Other relationsof electrolytic to ordinary chem ical action have already beendescribed .These facts show the intimate connect ion of chemical,electro chemical , and voltaic phenomena ; that the study of
( 23 )
electro-chemistry requires considerable knowledge of voltaicelectricity ; and that the modes of electrolysis require to beclassified according to the magnitude of the electric circuitsan d the degree of complexity of , the voltaic and electrolyticcombinations employed. Neither voltaic action nor electrolysiscan be successfully studied without also a previous knowledgeof general chemistry. As the subject of these articles iselectrolysis and not voltaic action, the latter will only be explained so far as is necessary to elucidate the former.
Mod es of Generation of Voltaic Curren ts — A voltaiccurrent may arise— First
,from the contact of two metals with
one liquid, e.g ., zinc and copper in dilute sulphuric acid ;
second,from the contact of one metal with two liquids, e.g .,
two pieces of silver, one in a solution of potassic cyanide, and
the other in argen td cyanide of potassium,the two liquids
touching each other through an intervening porous partition, .or by lying upon each other or third; from the contact of two ,
metals with two liquids so arranged, e.g., zinc in dilutesulphuric acid, and copper in a solution of cupric sulphate.The strength of current thus obtained is usually the greatenthe more wide the difference in the chemical properties of the,
metals and liquids employed,and is commonly the greatest
with the combinations of two metals with two liquids.
Source of’ the,Current — Th eory of Voltaic Action — Two
rival theories of the source of the current have long beenentertained— Fi rst
,that of Volta
,that the current is due to
contact of dissimilar conductors of electricity ; and ~ second ,that Of Farad ay and other English investigators, that it is dueto chemical action. Neither of these views
,however
,is com
pletely satisfactory,or has been universally accepted.
If,however, we adopt a theory that the molecules of sub
stances (those of chemically active bodies in particular) are in a
state of ceaseless motion (that of frictonless bodies in a frictionless medium
,the universal ether) until they chemically unite, an
efficient cause of the current (and of chemical action) becomesat once exceedingly clear.According to this view, which I may term the CeaselessMolecularMotion Theory of voltaic and chemical action, neithercontact nor chemical action is the real dynamic cause of thecurrent, but the true cause is the potential molecular energyof the corroded metal
,and of the corroding element of the
liquid with which it subsequently unites,and chemical corro
sion is only the p rocess or mode by which the molecular motionsof these substances are transformed into heat and current.Both the heat and electric current produced during the
chemical corrosion of metals by electrolytes are recognisedmodes of motion , or forms of active molecular energy
,and as
motion or energy cannot be created, bu t can only result from
( 24 )
the expenditure of some other form of motion, these movements are derived from the original metal and liquid
,and the
corroded metal and liquid employed have,after the action
,lost
to a greater or less extent their power of further producingheat or current.According to this view
,also
,contact is only a static condition
which enables the molecular motions of the one substance tomodify those of the other
,and thus produce static electric
polarity ; and this, i f sufficiently strong, produces corrosionand the new modes of motion
,namely
,heat and current.
Electrical Th eory of Chemistry.— This theory (attributedto Berzelius) assumes that the chemical union of any two subs tances is an electrical act ; i.e., that during contact, previousto union
,the one substance is relatively positive, and the other
relatively negative, and that the act of union is a consequenceo f these states ; also that during the act of union the twoelectric states neutralise each other and produce heat andc urrent.In accordance with this theory, and with the voltaic series
O f metals, the various elementary substances have beena rranged in the following order, the most strongly electro
p ositive substance being placed first, and the most negativeI one last z— Caesium,
rubidium, potassium, sodium,lithium
,
barium,
strontium, calcium, magnesium,aluminium
,zinc
,
cadmium,iron
,cobalt, nickel, lead , tin, copper, mercury,
silver, pallad ium, gold, iridium, rhodium, platinum,hydrogen
,
osmium,an timony, tellurium, arsenic, silicon , carbon, phos
phorus,selenium
,iodine, bromine, chlorine, n itrogen , sulphur,
‘
iluorine, oxygen.The electrical theory of chemical action may be reasonably
extended from that of metals and electrolytes to that of alln on-conducting elements in non-conducting liquids
,because
assistance to conduction is only of degree, and not infinite.I f
,th erefore , the electric polarity produced by the molecular
motions of bodies is suflicien tly strong, and the electricalcircui ts sufliciently small
,chemical union and electrolysis in
non-conductors must occur.The deposition of copper and silver from aqueous solutionsof their salts by immersing in them a piece of ordinaryphosphorus
,are good examples of electrolysis produced by a
non-conducting element in conducting solutions,and the
separation of hydrogen from pure water by contact of a zinclatinum couple is an instance of electrolysis by conductingbod ies in a non-conducting liquid. And the chemical decomposition of non-conducting liquids by non-conducting elementsmay be regarded as only an extension of the same kind of ac tion.
Voltaic Series.-; The degree of power of generating avoltaic current differs with every different ,
metal and liquid.
molecular motions of the two metals act upon each other andthe composition of forces causes the one metal to becomepositive and the other negative ; also that, when a metal isbrought into contact with an electrolyte, similar effects Of
polarity occur.Previously, therefore, to the completion of the circuit andformation of a current, the two metals, by contact with anelectrolyte
,become charged with the two kinds of electricity:
in a statical condition, and are in a state of electric potentialor pressure, capable of doing electric work by their subsequent discharge. This difference of electric potential produces electric flow, like a difference of pressure of water produces a flow of that liquid. The electric charges of themetals are in a state of tension tending to escape , and may bedetected by means of an , electroscope or measured by anelectrometer the deg ree of ' tension is, however, exceedinglyminute. The charged state also produces induction, whichacts from molecule to molecule duIing discharge, and precedescurrent.Electromotive force, or the power which moves, or tends to .
move,electricity from one place to another, varies with every
different voltai c couple, and with the same couple at every '
different temperature ; and these differences may be detected .by opposing the two c ouples in be compared, in single seriesin circuit
,with their terminals connected to those of ag alvano
meter the current from the strongest then produces a deflection of the needles. In a voltaic series, the metals are arranged .
in the order of their relative degrees of electromotive force.
The degree of electromotive orce of a couple depends considerably upon the degree of difference of strength of chemical .
affinity of th e two metals for the electrd neg ative elements ofthe liquid ; and the farther asunder the metals are in the
'
chemicO-electric or volta tension series, the greater usually isthe electromotive force of th e current they produce. Allother circumstances being alike, the most rapidly corroded ,
metal, used with the least corroded one, usually gives thecurrent of greatest electromotive' force.
The measurement of the degree of electromotive force of a ’
voltaic cell is usually made by c omparing it with that of someconven ient and steady source of current
,su ch as that of a '
Daniell or a Clark cell. The unit of electromotive force (E) istermed a volt, that of a Daniell cell is 1078 volt
,and that
of a Clark volt. For measuring feeble electromotive ’
forces I have devised a convenient form of thermopile , consisting of about 300 pairs of iron and German silver wires :
and have employed it in making a great number of measurements
,not much exceeding that of one Daniell. It is capable of
measuring diflerences of m m of a volt. (Seof theBirm. Phil. Soc., VOLZ IV.
,Part
27
Resistance.— Every conductor of electricity,no matter how
good it may be, is an obstacle to the passage of a current.Electrolytes offer great resistance, especially with anodes composed of a metal which does not readily dissolve in them.
Perfectly pure water with platinum electrodes hardly transmi ts any current from a single voltaic cell. The degree o f
resistance of a saturated solution of sulphate of copper at48
°
F.— and this is a comparatively good conducting elec
trolyte— is nearly 1 7 million times that of a copper wire of
equal length and section at 32°
F. Tables of the conduction resistance of various l iquids are contained i n mostworks on voltaic electricity.According to Quincke (“ Pogg Annalen, Vol. CXLIV.,
pp. 1— 33, 1 61 as long as the density of the current inthe liquid is too small to overcome the chemical affinity theliquid will behave as an insulator
,but it may become con
ducting by an increase of that density. Liquids conduct,accordin g to Ohm’
s law, the same as solids (Journal ChemicalSociety, 2nd series
,Vol. X.
,.p
The total resistance in an electrolytic circuit is usuallydivided into internal, or that in the battery, and external, orthat m the remainder of the circuit
,there 1s resistance in the
battery itself,in the liquid , and especially at the surface of
the negative plate,if hydrogen is evolved there.
The ordinary unit of resistance (R) is termed an ohm,and
is that offered at 0° C. by 10486 metre length of mercury of1 square mi llimetre section. The amount of resistance in awi re
, A, is conveniently measured by dividing the currentfrom a very small Daniell cell , so that one portion shall passthrough A and one wire, B, of a differential galvanometer, andthe other portion through another wire of known resistance, C,
and the other wire,D
,of the galvanometer in the Opposite
direction to that through B,and altering the length of A until
the needles of the instrument stay at zero. The resistancein A and C is then equal. The measurement of resistance ofan electrolyte is much
'
more difficult on account of the varyingpolarisation of the plates
,but may be effected in a somewhat
similar manner by making two measurements by means of avery feeble current after the polarisation has become steadyone when the electrodes are near together
,and the other when
they are far asunder,using in each case electrodes as large as
the transverse section of the liquid, and m certain cases of thesame metal as that of the salt of the electrolyte in order todiminish polarisation. The difference of resistance of the twomeasurements is the amount of resistance of the difference oflength of liquid m the two cases.
Streng th of Current — The strength is the amount whichflows through any transverse section of the circuit in a given
( 23 )
period of time,and the amount flowing at any given instant
is the same in every such section of the circuit,whether
that section be large or small ; the unit of time employed isone second. It varies directly as the electromotive force
,and
inversely as the total resistance in the circuit (Ohm’
s law).A given voltaic cell can only yield a certain maximum
strength of current,and any conductor introduced into the
circuit diminishes that amount. The greater the electromotiveforce of a current, the less is i t diminished by increase ofexternal resistance ; such a current is said to possess “ greatin tensity.”If the extern al resistance is very small, an increaseof electromotive force of the battery adds very little to thestrength of the current ; but if i t is large, the Opposite effecttakes place. The difference of effect produced by means of acurrent from a single cell
,and one from many
,does not arise
from any difference in the nature of the current in the twocases, but from the difference of proportion of internal toextern al resistance. No difference has hitherto been provedto exist in any two currents of equal strength.The unit of strength of current (I) is termed an ampere,and is the strength produced by an electromotive force of1 volt in a circuit having a resistance of 1 ohm. The strength
(or quantity per second ) of a current may be measured bypassing the current during a known period of time, either bymeans of platinum electrod es through dilute sulphuric acidin a voltameter
,and measuring the evolved hydrogen, or by
means of silver electrodes through a solution of argentocyanide of potassium, containing the minimum practicableamount of free potassic cyanide
, and weighing the depositedsilver. The latter method gives a little deficiency, owing toa small amount of the current passing through the freecyanide. Each 000162 grain of hydrogen or 017 343 grainof silver deposited per second equals 1 ampere. Additionalmethods of measurement are usually described in text bookson voltaic electricity.
Unit of Quantity of Current — VVhilst the degree of intsusity of chemical action between two substances determinesthe electromotive force of the current, i t is the quantity ofsubstances uniting which determines its amount. The unitof quantity of current (Q) is termed a coulomb it is one verylittle used , and is the amount which a strength of one amperegives in one second. Measured by the method of electrolysis,it is that which deposits 000162 grain of hydrogen, 005 1035grain of copper
,or 017343 grain of silver.
Density of Current — This means merely the strength ofcurrent passing through a given section of a conductor, or intoor out of a given sized surface of electrode. No unit of ithas hitherto been commonly recognised, but I have proposed
( 29 )
(Free. of Birm. Phil. Soc., Vol. III., p. 277) the unit strengthof current entering a surface of one square centimetre ofcathode as a convenient one.Density of current at the surface of the electrodes is one of
the most important circumstances in electrolysis. Variationof i t has often great effect both upon the physical structureand chemical composition of deposits upon cathodes ; theformer has already been described. It also appears to affectthe properties of oxygen and chlorine when they are separated at the anode. Metals which are easily oxidised
,such as
cobalt, are deposi ted upon cathodes in a state of oxide orbasic salt if the density of the current at that surface is small
,
but in the state of metal if it is great. It was largely byincreasing the density of the current that Davy succeeded inisolating potassium. Any circumstance, such as polarisation
,
wh ich diminishes the d ensity of the current,is liable to affect
the properties and composition of the deposit.Quincke has shown that the force tending to separate the
elements of an electrolyte is proportional to the strength ofthe current per unit of sectional area of the liquid ; that itincreases with the electromotive force of the current, and isinversely proportional to the length
,but independent of the
cross section and conductivity of the liquid,if the resistance
of the remainder of the circuit is small in comparison withthat of the electrolyte (Journal of the Chemical Society,Vol.X.
,p.
Distribution of Current in Electrolytes — With a perfectly homogeneous electrolyte of much larger section thanthe opposed surfaces of the electrodes
,and the latter placed
centrally and symmetrically in it, when the current leavesthe anode it spreads out in the liquid in
'
curves not unlikethose of magnetism diverging from the poles of a magnet,and the densest portion of the current is in the central axisjoining the electrodes. Its distribution in the liquid hasbeen investigated by Tribe, who suspended little bits ofmetal in different parts of a cross section of the solution,and ascertained the amount of electrolytic action producedupon them by the same current, during the same period
(Proceedings Royal Soc., Vol. XXXI., p. 320; Vol. XXXII.,p. 435)Relative Amounts of Currents produced by Different
Metals — Equal weights of different metals yield by voltaicaction different amounts of current. Whatever amount ofcurrent a particular weight of any given metal requires inorder to deposit it
,that same amount will it yield by voltaic
action ; its generating and consuming powers in relation toelectric current are therefore equal. The amount of currentproduced by a given weight of a particular metal depends
( 30 )
,both upon‘
the atomic weight and upon the degree of valency,Of the metal. An atomic weight of a monadmetal yields oneequivalent quantity of current ; one of a dyad yields two ; atriad three ; and so on.The percentage of equivalent of external current actually
obtained is, however, in practice extremely variable, and thefull proportion is rarely obtained. This arises from the circumstance that a greater or less proportion of the currentgenerated circulates in minute local circuits upon the surfaceof the dissolving metal, and does not enter the external circuit at all. By actual experiment in nearly one hundredcases of various kinds, I found that the proportion of externalcurrent varied from about 2 to nearly 100per cent.
Electrolytic Arrang ements. — Various combinations anda rrangements have been employed in which chemico-electriccurrents produce electrolysis ; and these arrangements havebeen classified as follows — 1 . Electrolysis by simple contactof onemetal with one liquid 2. By contact of one metal withtwo liquids 3. By contact of two metals with one liquid 4.
By contact of two metals with two liquids ; 5 . By a separateelectric current and By a separate current and a series ofelectrolysis vessels.The first of these arrangements is termed the “
simpleimmersion process,
’ ’ the most familiar example of which 13 thecoating of iron with copper by simply dipping it into a solution of cupric sulphate. In this process the voltaic currentsare excess ively minute , are generated i n immense numbers atpoints inconceivably small all over the immersed surface of themetal
,and re enter producing electrolysis at all the inter
mediate points of that surface. In this arrangement theactions and products at the anodes cannot conven iently beobserved or separated from those at the cathodes. The depositof metal obtained by it is usually very thin.The second consists in either carefully placing a lighterliquid in a distinct stratum upon a heavier one
,or separating
the two by means of a porous partition,an d immersing the
metal in contact with the two liquids. The portion of metalin one liquid then generates a current which re-enters the
‘ other part,or the second piece of ' the same metal in the second
liquid , and produces electrolysis. By this contrivance thenegative portiOn of the metal receives an electrolytic depositin a liquid which the metal itself is unable to decompose bysimple contact.The third consists in bringing two metals into contact attheir upper ends, either without or by means of a wire, andimmersing their lower ends in the liquid ; or allowing themetals to touch each other in the solution. Under these circumstan ces a current passes from the p ositive metal through
1 31 )
the liquid into the negative one, preducing electrolysis, andreturns by the external circuit ; the positive me tal also actssimultaneously by
,
“simple immersion process.”This con
trivance also enables the negative metal to receive an electrolytic deposit in a liquid which it does not decompose by“simple immersion
,
’ because the second metal offers a secondpath of return for the re entering current. Cases of selfd epositing metals acting by this process have long beenrecorded
,in which a metal immersed in a solution of the
same metal has produced a metallic deposit, e.g ., with cadmiumin contact with copper in a boiling hot saturated solutionof cadmic chloride the copper becomes coated with that metal.These cases have been but little investigated. Under thisarrangement may be classed the
“ two metal couples ofGladstone and Tribe, in which the resistance is greatlydiminished
,and therefore the strength of the current in
creased , by making the circuits indefinitely small. This iseffected by electrolytically depositing copper, silver, orplatinum m a porous spongy layer upon the surface of zinc orm agnesium
,washing the plate so prepa1ed , and immersing it
in the liquid to be electrolysed.The fourth is termed the “
single cell process, and consistsof two liquids separated by a porous partition, the two metalsbeing partly immersed, one in each liquid, and in contact witheach other externally
,or connected together outside by means
of a wire. This method also enables a deposit to be producedu pon a metal which does not decompose the liquid by simplecontact. In this and the second arrangement, however, theliquids gradually diffuse into each other, waste the positivemetal by simple immersion process
,
“ and disturb the action atthe negative surface.”The fifth 1s the most convenient arrangement, and the mostfrequently employed. It consists of a vessel containing theelectrolyte and two electrodes
,neither of which spontaneously
d ecomposes the solution,the electrodes being connected with
the battery or other source of current by means of two -wires.It is -known as the “ battery process
,or “
separate currentprocess”By it the strength of current in relation to theresistance in the electrolysis cell may be indefinitely increased,the most incorrodible metals may be used as anodes, and witha sufficiently dense . current and suitable liquid even the alkalimetals may be deposited. The s ixth arrangement consistsmerely of a single series of such vessels and electrodes with anundivided current passing through the whole of them. It 1snot much employed.
Self-Deposition of Metals.— Raoult, also Gladstone andT11
'
be, have discovered some new cases of electrolysis of this kind.Raoult states (ComptesRendus, Vol.LXXV.,
p. 1 that when
32 )
two plates, one of copper and one of cadmium,are completely
immersed in a solution of cadmic sulphate deprived of air,and
covered with a layer of oil, as long as they do not touch eachother, a very slight evolution of hydrogen is seen on thecadmium plate , whilst the copper shows no visible change.When
,however
,the plates are caused to touch each other
,
cadmium at once begins to be deposited on the cepper one.Couples of gold iron, gold nickel, gold antimony, gold lead ,gold copper, or gold silver, immersed either in cold or hot acidor neutral solution of salts of the more positive of these twometals
,yielded no deposit of that metal (Journal of Chemical
Society, 2nd series,Vol. XL, p. Gladstone and Tribe
also observed that a copper zinc couple separated zinc from aper cent. aqueous solution of zinc sulphate (ibid. p.
Other instances of self-deposition will be given.As these deposi ts of cadmium and zinc did not appear in
solutions of the nitrates of those metals, and as an oxide ofmetal appears to be formed upon the corroded or positiveplate, a probable explanation of the formation of the metalli cdeposi ts is that the water is decomposed, the salts in contact wi th the negative plate are reduced to the metallic stateby the nascent hydrogen, and the acid thus formed is prevented from corroding the deposi ted metal by being immediately removed from i t by diffusion into the mass of theliquid. Another arrangement in which a metal depositsi tself is well known. It is that in which one metal is in contact with two different liquids, one of them being a solutionof a salt of that metal.
Methods of Preparing Solutions . for Electrolysis — The
exact details of preparing solutions for electro-chemicalaction differ of course in every different case. There are
,
however,two general methods— the one termed the chemi cal
,
and the other the battery or separate current process. In theformer the usual processes of oxidation
,crystallisation , solu
tion,&c., are employed , and may be found sufficiently
described in any work on general chemistry. The latterusually consists in taking a suitable solvent
,hanging in it a
large anode of the particular m etal and a proper cathode,and
passing a current until sufficient of the metal is dissolved andthe liquid yields the desired deposit. The liquids obtainedby the two processes, however, are not always exactly the
same in chemical composition, because the electric process isattended by chemical changes at the cathode. In the latterprocess the anode is sometimes immersed in a portion of theliquid in a porous cell, the latter being partly immersed in theremainder of the solution.
Electro-Ch emistry of Individual Substances.— Usually,electro-negative bodies appear at the anod e, and electro
( 34 )
I t is separated by all the electrolytic process es. ~Its l iberation and s ubsequent spontaneous ignition when potassium is
placed upon water is one'
of the most familiar and striking ex
periments of electro-chemistry. Magnesium, and especiallyits amalgam -with mercury, decomposes watery setting freehydrogen. The same metal also liberates hydrogen from a
great variety '
oi saline solutions. Nearly all the readilyoxid able metals decompose acidulated water, and the in
stances are So numerous that to specify all of them is quiteunnecessary.
'
According to H.St. Claire Deville, silver evolveshydrogen rapidly from aqueous hydriodic acid ; and evensilver, gold , and platinum,
when in a finely divided state,
l1b erate hydrogen from a hot concentrated solution of potassiccyanide.I have observed the following cases relating to separation of
the g as bymagnesium: Th at metal did not evolve hydrogenby simple immersion in dilute hydrofluoric acid , and only a
little in an aqueous solution of potassic chloride,but evolved
it freely in a mixture of the two liquids. Similarly with thesame acid and a solution of chlorate of potassium. It did notevolve the gas in a mixture of the same acid and a solution ofpotassic perchlorate. It set free hydrogen from a mixture ofthat acid and a solution of potassic bromide ; but not fromeither alone. Similarly with magn esium in hydrofluoric ac idmixed with solution of potassic iodide but not with that acidwhen in admixture with solution of potassic iodate. It setfree hydrogen from a mixture of that acid and solution ofpotassic sulphate but not from either liquid alone. Probablythe absen ce of gas was due, in some of these cases, either tothe'formation of a film of magnesic fluoride or suboxide uponthe surface of the metal, and the inso lubility of that salt in the
drous hydrofluoricwas freely deemnpésed but anhydrous hydro
chloric acid , liquefied by great pressure at 0°
C.,scarcely con
ducted at all, and evolved no visible as.
Nearly all aqueous acids yield hydrogen at the cathode bythe separate current process. This accords with G.
‘ Wiedemann
’
s ' observation, that mixed liquids are more easily electrolysed th an unmixed ones. According to Bourgoin, byelectrolysis with platinum electrodes of distilled water containing pure sulphuric acid, the hydrogen and oxygenobtained are probably not results of an action of the currentupon the water; nor of liberated electrolytic products actingupon thewater, but
'
of direct decomposition of a hydrate ofsulphuric acid. Concentrated n itric acid d oes not liberatehydrogen by electrolysis, the hydrogen being absorbed.
( 35 )
Aqueous solutions of alkalis frequently yield hydrogen atthe cathode. The electrolytic behay iour of each of theindividual acids
,salts
,and alkalies
, with regard to separationof hydrogen, &c., will be more fully described under the
heading of the respective substances.In consequence partly of the very frequent simultaneous
deposition of hydrogen with other metals,these metals ofte
contain that gas. It . has been observed conspicuously indeposited palladium
,and
, to a less extent, in iron, cobalt,nickel
,copper
,and tin
,and it has been stated that the
explosive variety of deposited antimony contains hydrogen“
;but
,according to E. Pfeifer
,
“ explosive antimony containsno free , hydrogen (Jour. Chem. Soc.
,Vol. XLII., 1882
,
p. Much,
'
however, depends, in all these cases , uponthe kind of solution employed. I have several times observedthat the steel blade of a knife which has been used as a
cathod e for a short time,either in a dilute acid, or in an
alkaline liquid , becomes very brittle. Other investigatorshave also noticed that the simple immersion of iron in adilute acid greatly reduces its tenacity and it is not improbable that steam boilers are sometimes weakened by theirdecomposing the water and absorbing the hydrogen. It hasbeen stated by Bettyer that if a piece of palladium,
cobalt,nickel
, or\tin
,has a wire of aluminium twisted round it, and
is then immersed during a few minutes in a dilute acid,it
absorbs sufficient hydrogen to exert a slightly reducing actionupon a solution of potassic ferricyanide, also that a plate ofpalladium,
previously coated with palladium black, absorbsthe gas more rapidly, and when taken from the liqu id andd ried quickly between porous paper becomes red hot in theair in a few seconds.For the absorption of hydrogen by platinum in electrolysis,
see Jour. Chem. Soc., 1877 , Part II., p. 161 , and for the deposition of hydrogen on both electrodes see ibid. Part I., p. 678.
Separation of Oxyg en — O. Electro chemical equivalent=T
= 8. A dyad anion. It ismuch less frequently or readi lyobtained than hydrogen
' by electrolysis, also less easily thanthe least oxidable metals. It is not separated by either ofthe electrolytic methods
,except those m which a separate cur
rent is employed. To obtain it requires not only a separatesource of current
,but also an anode and liquid not easily
oxidised. It 1s usually obtained by passing a current bymeansof platinum plates through a cooled mixture of one volume ofsulphuric acid, and three to five volumes of pure water. Thegas thus obtained 1s partly 1n the state of ozone
,whichmay
be detected by its odour. Numerous other mixtures of water"
with some acid, alkali, or salt, to render the mixtureconducting, might be employed for obtaining it, but in all cases”
11 2
1 36 )
theanode must be a non-corrodible one. The electrolysis ofvarious substances such as fused oxides
,&c., which yield
oxygen, will be described in their appropriate places.
Electrolysis of Water. 0. Molecular weight 18.
F. Kohlrausch has shown (Ding er’
s Polytechnik Journal, Vol.‘
222, p. 283) that perfectly pure water is practically a non
conductor of the voltaic current (and probably not an electrolyte), and that on the addition of the least trace of impurity its conduction-resistance is greatly diminished.Pure water is rapidly decomposed by simple immersion orcontact of either of the alkali metals
,less rapidly by alu
minium amalgam and by magnesium,and slowly by the
ordinary base metals, in each case by oxidation of the immersed metal. Magnesium amalgam containing one hal f a percent. of magnesium decomposes water with violence
,and more
rapidly than sodium amalgam containing twice that r
centage of sodium (Cailletet, Watts’
s“Die. of Chem , 5211
VI., p. An amalgam of aluminium and mercurydecomposes water at ordinary temperature (A. Cossa, Watts
’
s
Die. of Chem ,
”Vol. VII., p. Al loys of aluminium andgallium decompose water readily, setting free much hydrogenand nearly the whole of the gallium as liquid metal (Lecoq deBoisbaudran , Chem. News
,Vol. XXXVII., p. Finely
divided iron slowly decomposes boiling water,and sets free
hydrogen (E. Ramann , Jour. Chem. Soc., Vol. XL., 188 1, p.
Water containing certain acids is decomposed morerapidly ; boracic acid , cyanide of mercury, sugar, or gum d issolved in it have but h ttle effect. The decomposi tion of watercontaining sul huric acid
,by means of zinc, is a common mode
of obtaining hydrogen. Iron filings wetted with water, andexposed to the air or nitrogen at GO
°
F.,induce the formation
of ammonia (Berzelius).‘Gladstone and Tribe state that pure water may be decemposed by a
“ copper-zinc couple, also by iron or lead whichhas been previously coated electrolytically with spongy copper.At 0
°
C. the decomposition of water by a zinc-copper couple isnearly nil; but at 100
°
C. i t is very great (Jour. Chem. Soc.,Vol. XXXV.,
187 9, p. With a magnesium platinumcouple the decomposition is vigorous, even in cold water
(ibid . p.According to D. Tommasi, water is not decomposed by a
separate current from a single zinc-carbon or zinc-copperelement if the electrodes are of platinum ; but if the anode isa metal— copper, for instance— which , under the influence ofthat current
,can unite with oxygen, the water is decomposed
(e . Chem. Soc., Vol. XLII., 1882, pp. 134 andThe usual mode of electrolysing water is by previously
mixing sulphuric acid freely with it, a nd passing a separate
( 37 )
current through the mixture by means of platinum electrodes ; by this method its oxygen as well as its hydrogen isobtain ed, and a small quantity of the former gas is absorbedby the water. The oxygen contains a small proportion (butnot more than fi t part of its weight) of ozone.Janeczek considers that in the electrolysis of pure water,hydrogen at the cathod e and hydric peroxide at the anod e arethe proximate resultants, and that the peroxide is resolvedinto water and oxygen (Jour. Chem.Soc., 1 876, Part I., p.Bouvet electrolysed water under a pressure of several
hundred atmospheres. He found th at the amount of waterdecomposed by a given quantity of current was independentof the pressure (Jour. Chem. Soc., Vol. XXXVI., 187 9, p.Water containing atmospheric air yields ammonia at the
cathode,and nitric acid at the anode (H.Davy).
Separation of Oz one — Ozone is developed by electrolysis .
in aqueous solutions of nitric, hydrofluoric, sulphuric, or phosphoric acids, also in those of nitre, potassic phosphate, or sodicsulphate
,but not in those of hydrochloric or hydrobromic
acids, or in strong nitric acid,or in aqueous solutions of
metallic chlorides,bromides
,iodides, or ferrous sulphate.
According to Houzeau (Comp tes Rendus, Vol. LXXIV., p.the electrolysis of water furnishes only 3 to 5 milligrammes ofozone per litre (Jour. Chem.Soc., Vol.X.
,2nd series, p.
Electrolysis of Hydric Peroxide.— H202. Molecular weight
34. Electrolysis g radually resolves peroxide of hydrogeninto hydrogen and oxygen
,the proportion of the latter being
greater than in the decomposition of water (Thenard).E. Schone has electrolysed peroxide of hydrogen, and foundthat the results were influenced by the strength of the solution
,the degree of acidification
,and the strength of the
current,and concludes that it is not an electrolyte, and that
its decomposition during electrolysis of the water or acid
present is a result of secondary action, due to the liberatedydrogen and oxygen (Jour. Chem. Soc., Vol. XXXVI., 1879,p. 878)According to Berthelot a dilute solution of hydric peroxideundergoes electrolysis in two different ways— viz., one with,and one without
,the evolution of hydrogen
,and both of
these may coexist. With high electromotive force both gasesare evolved , but with low electromotive force, such as that ofa zinc cadmium couple
,only oxygen is given off, and no
hydrogen gas appears at the cathode. The latter decompositiou can be effected by any current
,however feeble. In this
case either the peroxide splits up into water and oxygen, ormore probably a secondary action occurs, and the electrolytichydrogen combines with undecomposed peroxide to form
aration of Nitrog en. —N. Electro chemical equivalent
366. A triad anion. It is set free (along with other
gases) by simple contact of metallic zinc with ammonic nitratein a state of fusion. A concentrated solution of ammonia,when electrolysed by a separate current and iron electrodes
,
yields pure n itrogen at the anode,and hydrogen at the
cathode (Hisinger and Berzelius).The electrolysis of compounds of n itrogen and hydrogen
will be treated of with the alkali metals.
Elec trolysis of Oxides,of Nitrog en — The only ones oi
these which appear to have been thus treated are hyponitric(N 04) and ordinary nitric acid (HNO3 The former aqueousaci conducts slowly
,and is decomposed (Faraday).
Z orn prepares hyponitrites by the electrolys1s of a solutionof a nitrite bymeans of a current from four Bunsen cellsahd mercury electrodes, and stopping the current as soonas ammoni a begins to be evolved In this reduction hydroxylamine is also formed (Jour. Chem. Soc., Vol. XXXVIII ,1880, p.Nitric acid when concentrated is a good conductor. It
yields with platinum "electrod es oxygen,and simultaneously
becomes yellow and then red at the cathode, and finally evolves
g aseous nitric oxide. Amore dilute acid yields hydrogen atthe cathode, the quantity being greater as the acid 1s weakerand the current more dense ; and if the acid 13 not of greaterspecific gravity than 1 24 and the current not too strong , thewater alone of the acid 18 decomposed, and the full equivalentquantity of hydrogen is set free as gas.B electrolysis concentrated nitric acid is decomposed with
prodyhction of n itrous acid ; with the acid of sp.gr. 1 2 a feeble
current does not produce this effect. No ammonia is producedin d ilute nitric ac id , either per se or in presence of sulphuricacid ; but if a solution of cupric sulphate is added 1n sufficientamoun t, sulphate of ammonium and metalli c copper are simultaneously produced until all the nitric acid is converted intoammonium sulphate. In the presence of free alkali, nitratesare not converted into ammonia
,but the
,latter is oh d
into nitric acid (C. Luckow,Jour. Chem. Soc., Vol. ,XXXVfil.
1 880,p.
.Brester states (Chem. News, Vol.KVIIL, p, ~144) that whendecomposed by electrolysis nitri c acid does not evolveanyhydrogen gas at the surface of a cathode of platinum or charcoal ; the acid is converted into ammonia. Bloxam (ChemNews, Vol. XIX. ,
p. 289) has shown that the hydrogen set freefrom a cathod e of platinum .in dilute nitric acid, or in a solution of potassic nitrate, contained in a porous cell, placed indilute sulphuric acid containing the anod e, converts not morethan one-half of the nitric acid of either of those solutions into
( 39 )
ammonia. Bourgoin.(Comptes Rendus, Vol. LXX.
,p 8 11) has
also electrolysed nitric acid.The electrolysis of nitric acid, and solutions of its soluble
salts with electrodes of wood charcoal or gas carbon yieldmellog en free from nitrogen (Bartoli and Papasog li, Jour.Chem.
XLIV., 1883, p. 592; TheE lectrician, Vol.X., p.388 ,Vol. XI. pp. 28 andIn theelectrolysis of red fuming nitric acid n o gas is set
free at first at either electrode. At the anode, NO is totally:
changed to NO5by oxidation. At the cathode , NO5 is
reduced to H3N5
during the whole of the electrolysis (A.
Brester, Chem.
3
News,Vol. XVIII" p.
Finely divided copper,palladium
,platinum
,or carbon
,
charged with hydrogen,convert nitre into potassic nitrite
and ammonia (Gladstone and Tribe, Jour. Chem. Soc., Vol.XXXIII.
,187 8 , pp. 306 and Gladstone and Tribe
have also investigated the electrolysis of a solution of
potassic nitrate by a zinc copper c ouple, and are inclined tothe hypothesis “ that the two metals electrolyse the nitrateof potassium
,with formation of nitrate of zinc
,the redue
tion being effected at the negative pole throug h the agencyof the potassium”(Jour. Chem. Soc., Vol. XXXIII., 1878p. Professor Thorpe also has shown that the copperzinc couple
,in the presence of water and saltpetre
,converts
the whole of the nitrogen o f the salt,
first into nitrite andthen into ammonia (Jour. Chem. Soc.
,Vol. XXXIII.
,1 8 78 ,
p,
Passive State of Metals. -A peculiar condition, termedthe pass ive state
,occurs wi th various metals when used as
electrodes 1n nitric acid. By the following methods a platinumwire
,to be used as the cathode in nitric acid of 1 49 sp.
"
gr.,and in which
,with a suitable density of current, i t would
usually evolve gas for a time only, will be caused to evolve no
g as from themoment of immersion. 1st. By connecting andthen 1mmersing the two polarplatinum wires together 1n theliquid, and then at once separating them. (In this case, however
,the acid must be diluted with less than its own volume
o f water.) 2nd. By igniting the cathode, and then immersingit after the anode. 3rd. By taking a second platinum wire,and after the cathode has ceased to evolve g as, joining thewire to it outside the liquid, then immersing the Wire andWi thdrawing the cathode. The fresh cathode will then evolveno gas from the commencement, and this property may betransfexred by it to a third wire, and a fourth one, and so on.A wi re which has lost the power of liberating hydrogenrecovers it by exposure to air, the time required being longeras the acid is stronger. In all these cases , if the current istoo strong gas will be evolved. (Gmelin
’
s“ Handbook oi
( 40 )
Chemistry, Vol. pp. 253-362. See also A Brester, Chem’
.
News,Vol. XVIII., p.
Separation of Fluorine — F. Electro chemical equivalent19. Amonad anion. I have made many attempts with thisobject by electrolysing anhydrous hydrofluoric acid
,with
anod es of carbon, platinum,palladium,
and gold also by elec~trolysing certain fluorides in a state of fusion. In none ofthese cases, however, was that element definitely obtainedThese experiments will be briefly described under the headings of the respective substances.
Electrolysis of Anhydrous Hydrofluoric Acid. HF.
Molecular weight 20. I have examined this highly dang erous and
' extremely volatile liquid. It boils at 67°
F
Potassium immersed in the chilled acid evolved hydrogen, and'
produced vivid combustion. Sodium acted as i t does uponwater. The noble and base metals did not decompose i t.Magnesium, aluminium,
zinc,cadmium, tin , lead, reduced iron ,
powdered arsenic, antimony, or bismuth, did not expel hydrogen from it.I electrolysed the chilled fuming liquid by means of a
separate current with a platinum an ode ; i t conducted muchmore readily than pure water. With four Smee elements itbegan to conduct Visibly, and with ten i t conducted readily.NO '
od our of ozone was evolved. The anod e gradually ac
quired a thick red -brown crust,which deliquesced in the .
atmosphere. With forty elements the conduction was copious,the anode rapidl
ycorrod ed , and much finely-divided platinum
collected in the iquid. The brown coating was insoluble inthe acid
,but dissolved with formation of a basic salt in water,
and formed a blood-red liqu1d. With an anode of very closeo
g rained gas carbon, and six Smee cells,conduction occurred
freely,and the carbon rapidly disintegrated. Anodes com
posed of fifteen difl'
erent kinds of carbon of dense woods weretried with a current from ten elements ; those made fromkingwood , beech, ebony, boxwood , and lignum vitaewere thebest. On immersing them in the acid , even without a current,they evolved bubbles (of air cracked
,and flew to pieces
,
and on passing a current they broke immediately, some withv iolen ce, projecting the fragments and liquid in all directions— even the densest kinds behaved thus. The most resistinwas that made from beechwood. With much difficulty, anby the aid of a magn esium light , i t was ascertained that thepassage of the current was not attended by any increase ofbubbles from the carbon. No special odour besides that ofthe acid could be detected , but the charcoal , when removedfrom the liquid
,emitted a feeble chlorous od our, as well
that of ; the acid.
( 42 )
The anode was not corroded, and no gas was visible at thecathod e. By simi lar electrolysis with a current from ten
Smee cells of a mixture of equal volumes of“
30perc ent. pureaqueous hydrofluoric acid and strong hydrochloric ' acid
,
much chlorine was set free from the anode and h ydrogenfrom the cathode. This is consistent with the usual effectthat chlorides
,like oxides, are decomposed before fluorides.
Amixture of equal volumes of the aqueous acid and strongoil of vitriol yielded much oxygen and a strong odour ofozone at the anode and hydrogen freely at the - cathode.The anode ' corrod ed very slowly, and fumes were evolvedwhich rapidly blackened gutta percha. With selenious acidin place of the sulphuric, g as was set free at both electrodes,and much red selenium was depos ited upon the cathode. ~
No odour of ozone was evolved until a large quantity of redand black selenium had been deposited ; i t was then evolvedfreely. The anode was not corroded during twenty-eighthours’ free electrolysis; By electrolysis of the dilute hyd ro“fluoric acid, to which some phosphoric anhydride had been .
added , ozone was evolved from the anode and hydrogen fromthe cathode the anode was also slowly corroded.Bartoli and Papasog li have also el ectrolysed aqueous hydro
fluoric acid with anodes of wood charcoal or g as carbon, andfound the anodes disintegrate (TheE lectrician, Vol. XL , pp.28 .
and 101 Jour. Chem. Soc., Vol. XLIV., 1883, p.
Separation of Chlorine — Cl. Electroc hemical equivalentAm onad anion. Set free on passing
,by means of an
anode of carbon or platinum, an electric current through concen trated hydrochloric acid, or through aqueous solutlons ofthe chlorid es of sodium, ammonium, or other metals , alsothrough various chlorides in a state of fusion. With aqueoussolutions, some of the chlorine usually dissolves in the liquid.The electrolysis of chlorine water yields hydrochloric acid atthe cathode and a little chloric acid at the anod e (Balard ,also Connell, Gmelin
’
s“Handbook of Chemistry
,
”Vol. I.,p.
Electrolysis of Hydroch loric Ac id - HCI. Molecular weight365 .
_
I ascertained by experiment (Proc. Roy. Soc., May 4 ,1865) that the anhydrous substance, liquefied by great pres~sure, is a very feeble conductor of electricity. Two fineplatinum wires immersed in it fiths of an inch in length and
{Uth of an inch asunder, and connected with ten Smee elements,evolved no perceptible bubbles of gas, and produced only asmall deflection amounting to 23
°
of the needles of a sensitivegalvanometer ; and this amount of conductivi tymight possiblyhave been due to a minute trace of oil of vitriol mixed withthe liquid
,acid. In a second similar experiment
,with the.
wires {1
3th of an inch-apart, not the slightest conduction
( 43 )
occurred"
on“
using'
the same b at tery power, but by employing:the secondary current of a strong induction coil , with con !
denser attached, conduction and a steady deflection of 20
°
of
the needles took place, gas being freely evolved from the .negative wire only. It is evident, therefore, that liquefiedhydrochloric acid is a very
,bad conductor of electricity.
Bleekrode subsequently discovered (Proc.Roy.Soc., Vol. XXV.,
18 7 6, p. 325) that the anhydrous liquefied"acid “ opposes a
formidable resistance, and is not decomposed in a perceptibleway”by the passage through it of a‘
current from cellsof De la Rue’s chlorideof silver
‘
battery.
Gallium liberates‘
hydrogen freely by simple immersmn in
dilute hydrochloric acid (M. Lecocq de Boisbaudran ).E lectrolysis of concentrated h ydrochloric acid with a plati
num anode causes the anode to dissolve, but that of the; di1u teacid causes the formation of chlorine compounds at the anodewi thout corroding the platinum (D. Tommasi, Jour. Chem.
Vol. XLIV., 1883, p.In dilute solutions of metallic chlorides by electrolysis
hypochlorous acid is alone produced ; in concentrated o neschlorine is also set free. Chlorates are produced from thechlorides of the alkalies and alkaline earths
,as soon as the
reaction of the solutions has become alkaline, from the evolution of the chlorine and hypochlorous acid (0. Luckow,
Jour.
Chem; Soc., Vol. XXXVIII., 1880, p. If dilute chloridesolutions contain a little free hydrochloric
'
acid , hypochlorousacid is alone produced
,and the solution
,after a time,
‘
acquires
an alkaline reaction.The elect rolysis of aqueous solutions of certain metallicchlorides by means of the contact of two m’etals has ‘ beeninvestigated by Gladstone and Tribe (Phil. Mag.
‘Vol.XLIX., p. and will be described under the head ings of.the respective metals ; Thorpe has
,shown that the copper
zinc couple reduces chlorate of potassium to chloride (Gladstone and Tribe; Jour. Chem. Soc.,
-Vol.XXXIIl z, 187 8 , -p.Platinum charged with hydrogen behaves similarly
'
p. but more powerfully.
Electrolysis of Oxid es of Chlorine — Very little has beendone in this part of the subject. Aqueous solution of oxidedi chlorine (0102) yields hydrogen at the cathode and a smallquantity
i
of oxygen g as and perchloric acid at the anode.(Count Stadion). I h ave
.electrolysed aqueous chloric and
perchloric acids with anodes of silver.
Separation'
of Bromine — Br. Electro chemical equivalent80. Amonad anion ; It r is separated in many cases when
aqueous solutions,
of bromides are electrolysed by means,of
a separate curren t ' and an . incorrodible anode ; A '
portion ofthe liberated bromine usually dissolves in the liquid
,-an
( 44 )
aqueous solution of bromineyields by electrolysis hydrobromicacid, and a mere trace of hydrogen at the cathod e , but nobromic acid at the anode. The water is decomposed (Balard ,also Connell, Gmelin
’
s“ Handbook of Chemistry
,Vol. I.,
p.
Electrolysis of Hydrobromic Acid — HBr.Molecular weight8 1. Bleekrode has stated (Proc. Roy. Soc., Vol. XXV.,
p. 323) that anhydrous hydrobromic acid is a non—conductor tothe voltaic current from eighty Bunsen elrmen ts. Theaqueous acid when electrolysed by a separate current liberatesbromine at the an ode and hydrogen at the cathode.
Electrolysis of Oxides of Bromine — I have been unableto find any record of any one having electrolysed either bromicor perbromic acids, or aqueous solutions of their salts.By immersing a sheet of aluminium in an aqueous solution ofbromic acid, I observed that hydrogen and bromine were setfree.
Separation of Iodine — I. Electro chemical equivalent=127. A monad anion. It is
,however
, sometimes separatedby secondary action at the cathode. According to Bleekrode
(ibid) li uid anhydrous hydriodic acid does not transmit anycurrent rom eighty Bunsen elements. Faraday observed thatby electrolysis, with a separate current
,of potassic iodide, or
i od ide of lead , in a state of fusion,iodine was set free at the
anode. A solution of iodine in water yields by electrolysissome hydrogen at the cathod e. The water is decomposed(Belard, also Connell, Gmelin
’
s“ Handbook of Chemistry,
”Vol. I., p.
Electrolysis of Aqueous Hydriod ic Acid — A concentratedsolution of aqueous hydriodic acid yields by a separate curren t,and platin um electrodes
,iod ine alone at the an od e ; but a
dilute one yields iod ine and oxygen (Faraday). Matteucciobserved that the stronger the current
,and the more dilute
the acid, the greater was the preportion of oxygen.If the solution of an iod ide be covered with starch jelly, the
cathode be placed in the former, and the anode in the latter,the starch is turn ed blue around the anode, even if the solution contain a much larger quantity of bromide or chloridethan of iod ide (Ste inberg, Jour.Pr. Chan , Vol .XXV.,
p. 288Watta’s D ictionary of Chemistry, Vol. III., p.Riche states (Com tea c dus
, Vol. XLVI., p. 348) that iod icacid (HIOS) is prod
j
uced by electrolysis of aqueous iod ine, oran aqueous solution of hydriodic acid. In the latter case theacid is simply oxidised to iodic acid by oxygen evolved by thedecompmition of water. Ih -the former case the iod ine isfirst crn '
rerted into hydriod ic acid,and then oxidised in th is
way
( 45 )
Electrolysis of Oxides of Iodine; &e. — By immersing a
sheet of aluminium in a solution composed of twenty-sixgrains of dry iodic acid and five ounces of water
,I observed
t hat much gas was evolved ; the metal acquired, a strongodour of absorbed iod ine, and had increased about 16 perc ent. in weight (Proc. Birm. Phil. Soc., Vol. IV., Part I.)A solution of one part of iodic acid and ten parts of water
yields oxygen g as at the anode and iodine alone at thec athode
,the latter being separated by secondary action of
hydrogen,liberated by the electrolysis of the water (Connell ).
According to Bufl", however (Ann. Chem. et Pharm ,Vol. CX.,
p. the iodic acid is resolved by the current into hydro
g en and iodic anhydride, which latter is decomposed by thewater
,thus producing iodic acid and free oxygen (Watts
’
s
“ D ictionary of Chemistry,”Vol. III., p. The electrolysis
o f periodic acid does not appear to have been yet examined.When an iron or copper plate
,or better
,a zinc and copper
plate, connected externally by a wire, are immersed in strongsolution of potassium iodate at 60° F., complete reduction topotassic iodide occurs. Potassium bromate is similarly reducedto bromide ; but potassic chlorate slowly and incompletelyt o chloride (G. Pellagri, Watts
’
s“D ictionary of Chemistry,
Vol. VIII., Part 2, p.
Electrolysis of Bromide of Iodine — When an aqueoussolution of starch and iodine, which has been turned yellow byd issolved bromine, is subjected to electrolysis, i t becomeso range coloured at the anode by liberation of bromine
,and
blue at the cathode by separation of iodine (De la Rive, Ann.
Chem. etPhys , Vol. XXXV., p.
Electrolysis of Iodides, Bromides, and Chlorides. —Byelectrolysis, iodine and bromine are separated from solutionso f iodides and bromides. Iodates and bromates are produceds imultaneously from the iodides and bromides of the metals.oi the two first groups
,especially in concentrated solutions.
When the solutions of the chlorides, bromides, and iodidescontain free alkali
,only chlorates
,bromates, and iodates are
produced. From the insoluble compounds of chlorine , bromine,and iodine
,with the metals
,suspended in dilute sulphuric or
nitric acid, the acid radicle appears at the anode and them etal at the cathode (C. Luckow, Jour. Chem. Soc., Vol.xxxvn 1.
,1sso
,p.
Separation of Carbon — C. Atomic weight = 12. Atetrad'
c ation. “An excess of silicon fused w ith potassic carbonatesets free carbon.”Deville states that metallic aluminiumliberates carbon from carbonate of potassium in a s tate offusion (Chemist, New Series, Vol.IV., p. .I have observedthe same with fused sodic carbonate. According to Phipson ,
( 46 )
magnesium lby contact with fused carbonate'
of sodium set freecarbon abundantly (Proc. Roy. Soc. 1 864
, Vol.KIIL , p. 217,also Chemical News, Vol: IX., p
'
.
The following are some experiments of m ine (Proc. Birm.
Phil. Soc., Vol.IV.) — A‘
fused mixture of 200grains of puresodic h ydrate, 170 grains of pure precipitated silica
,and
610 grains of the mixed anhydrous carbonates of sodiumand po tassium was electrolysed by means of a currentfrom ten Smee elements, with a sheet platinum anod e anda thick platinum wire cathode. Conduction was free
,and
much oxygen, which relighted"a red-hot splint
,was liberated
at the anode. Dark streams‘
flowed from the cathode,sodium
was also set free,and if the
’
cathode was only slightlyimmersed bubbles of vapour of sodiumwere omitted , and tookfire at the surface of the liquid. After one hour ’s action theplatinum anode had lost ‘37 grain in weight. The cathodehad a feebly adherent rough deposit of a dull j et black colourupon it. This deposit was subsequently washed and dried a
portion of it burn ed with a glow when heated to redness, andleft a minute residue of grey platinum ; it also deflagrated withfused nitre below a red heat
,and vividly by heating with
potassic chlorate. It did not dissolve‘
nor evolve any gas in am ixture of strong nitric acid and pure concentrated hydrofluoric acid. It was, therefore, carbon.As carbon was
'
not readily deposited from the fused car
bonates of potassium and sodium,whilst silicon was deposited
from fused silicofluoride of potassium,and as
“ an excess of
silicon fused with potas sic carbonate sets free carbon ,but
silicon with an excess of the carbonate liberates carbonicoxide
,
”the carbon liberated in this experiment may have
been a secondary result, and an effect of previously depositedsilicon reacting upon the fused mixture. It was Wi th theexpectation of this effect that I employed silica in the mixture.I also electrolysed in a platinum cup a fused mixture of
4752 grains of 97 1 er cent. sodic carbonate (containing as
impurity only water and 21 7 4 grains of borofluoride‘
ofsodium
,by means of the same current
,a sheet platinum anode
and thick platinum wire cathode. Conduction was free. Gas
arose from the an ode , and a small amount of black deposi tformed upon the cathode. After having been well washedthe deposit was dried , put on a platinum dish, and heated toredness ; it burned with sudden incandescehce until nearlythe whole was consumed. It was, therefore, nearly wholly
I electrolysed in a platinum cap a fused mixture of 274grains of pure sodic carbonate, 37 5 grains of pure potassiccarbonate, both anhydrous, and 206 grains from crystallisedboracic acid,at a red heat, by means of a curren t from eightSmee elements and platinum electrodes. There was free con
duction,much gas from the anode, and an instant jet ; black
deposit formed upon the cathode and could be burned off
at a red heat. Metallic sodium was set free at the cathode,
especially during deep immersion. The anode was soon muchcorroded
,and acquired a very smooth surface
,and platinum
was deposited upon the cathode. No free carbon was ultimately found.
Electrolysis of ~ Carbonic Anhydride.— CO2. Molecularweight=.
-44. I have examined (Phil. Trans.Roy. Soc., 1861)the action of a voltaic current on carbonic anhydride liquefiedby great pressure. With electrodes of thin platinum wire
1
1
6th of an inch apart
,and the liquid below 32
°
F”not theslightest conduction occurred with a current from forty Smeeelements
,and sparks from a Ruhmkorfi
'
coil, which passedthrough
~
g3 ths of an inch of cold air in an alternate portion of
the divided circuit,would not pass through the liquid. In
another trial,with the wires about 7
1
6 th of an inch asunder,
sparks from the coil, which were. passing freely through
f i nds of an inch of cold air in the alternate circuit, passedoccasionally through the cold acid and exhibited a pale bluecolour. The liquid is, therefore, a strong insulator of electricity. Bleekrode also (Proc. Roy. Soc., 1 876 , p. 325) triedthe same liquid with a current from 5
,540 chloride of silver
elements. A spark jumped between the poles, and the tubeexploded . He concluded that the liquid is a very bad conductor. Cailletet (Comp tes Rendus, Vol. LXXV.
, p. has
als o arrived by experiments at the same conclusion.I tested by experiment in an approximate manner the
relative degrees of conduction resistance of distilled water,
and of the same saturated with carbonic anhydride at 60°F.
and at atmospheric pressure. No conspicuous difference Wasobservable.I also passed an elect
'
ric’
current from four Smee elementsby means of platinum wires during one week through verydilute sulphuric acid in a large U glass tube, one leg of whichwas kept full of a mixture of carbonic oxide and carbonicanhydride gases. No carbon was deposited. Fumingsulphuric acid
,also a syrupy solution of phosphoric acid
,
were saturated with dry carbonic anhydride,and then electro
lysed by means of platinum wire electrod es and currents from1 12 Smee cells in single series
,no carbon was deposited
(Proc. Birm.Phil. Soc., Vol. IV“)Electrolysis with An od es of Carbon. -According to A.
Bartoli and G. Papasogli, .in liquids whdse electrolysis 1s notaccompanied by evolution of oxygen at the anode
,anodes of
wood charcoal, gas carbon , and graphite are not disintegratedor dissolved, or suffer any loss of weight. In those .in whichoxygen is evolved, those anodes are partly disintegrated
, and
( 48 )
partly oxidised to carbonic oxide and carbonic acid gases,together with other products ; graphite used in those liquidsn ever imparts a colour to the electrolyte, but anodes of woodcharcoal and gas carbon, previously purified , colour i t black.both in alkaline solutions and in those of certain acids ands alts, by the formation of a black substance which they termmellogen , the composition of which is represented by theformula CHH204 , together with traces of benzo—carboxylicacid ; graph i te anodes in those liquids produce graphitic acid01411203. In alkaline electrolytes, anodes of wood charcoal,
g as carbon, and graphite produce mellic acid CHHGO12 pyromellic acid CmHoOs i hydromellic acid C H 2
02,and another
body,apparently hydro-pyromellic acid, 8,0}l Jour. Chem.
Soc., Vol. XLIV., 1883, p. 5 92 The E lectrician, 01. XI., pp.
28 and For the electrolysis with electrodes of woodcharcoal
, gas carbon , and graphite, of solutions of hydrochloric,hydrobromic, and hydriod ic acids and their potassium salts,potassic cyanide
,sulphuric and nitric acids and their salts
,
hydrogen and sodium sulphite, arsenic acid, boracic acid ,alkaline hypochlorites
,permanganates, bichromates, and
chlorates,chromic acid , mellic acid , oxalates, formiates,
acetates, &c., and sodic pyrogallate , seealso the same papei'
.
Separation of Boron — B. Atomic weight 31, equiv. £
9
36 3. A triad cation. By contact of magnesium with bo racica cid in a fused state boron is set free (Phipson , Proc.Roy.Soc.,Vol. XIII., 1864, p. 217 ; also Chem. News, Vol. IX., p.Boron was first electro-chemically isolated by SirH.Davy.
He states that when boracic acid is exposed between two surfaces oi platinum, receiving at the same time all the action ofa current from 300 cells
,an olive brown matter is formed
upon the negative surface, gradually increasing in thickness,and finally becoming black. The isolated body is boron
(Chem. News, Vol. XII., p.
Electrolysis of Oxide and Fluoride of Boron.—Burckhard
s tates (Chem.News, Vol. XXL , p. 238) that pure boracic ac idin a state of fusion is a non-conductor. I found that bye lectrolysing pure borofluoride of potassium in a fused state,with platinum electrodes and a separate current, boron wasd eposi ted , and combined with the cathode, rendering the latterrough and brittle.
Separation of Silicon — Si. Atomic weight 28. A tetradc ation. According to Golding Bird (Phil. Trans. Roy. Soc.,1 837 , p. 37 ) silicon may be electro-d eposited from a solutionof its fluoride in alcohol. The kind of apparatus he employedwas a combination of one voltaic cell in undivided circuit,with a “
single cell apparatus,the silicon being deposited
u pon the negative platinum plate of the latter. I electrolysed
a nd the metal is deposited upon the cathode (Chem.News,Vol.
pp.‘
93 and 121 TheE lectrician, Vol. X.,p.
Hydrie Sulphid e. — H 8 . Molecular weight 34. Thissubstance wh en liquefied by great pressure does not appearto have been yet subjected to the action of an electric current.Its aqueous solution would no doubt yield sulphur at a platinumanode. When dilute sulphuric acid is electrolysed with azinc an ode and a
"
charcoal cathode, hydric sulphide is evolvedat the latter (Highton , Chem. News, Vol. XXVI., p.
Electrolysis of Sulphur Dioxide— SO,Molecular weight
64. This oxide, liquefied by pressure, does not transmit acurrent from 40cells. An aqueous solution of the gas yieldsulphur and hydro en at the cathode by the passa e of sucha. current (De la Bive, Gmelin’s “ Handbook of C emistry,
”Vol. II.
,p.
The electrolysis of its aqueous solution, HQSO , is notsimply a separation of the oxide into oxygen at the anodeand sulphur at the cathode. According to A. Guerout
(Comptes Rendus, Vol. LXXXV.,p. with a feeble cur
rent is produced at the anode and a yellow liquidat the cathode with a stronger one sulphur also appears withthe yellow liquid
,and with a still stronger sulphur alone is
d eposited at the cathode. Its electrolysis resembles that of asalt
,the acid and oxygen b eing set free at the anode, and the
hydrogen (112) appearing at the cathode, where it acts upona fresh portion of the acid , and reduces it thus — H
2+
O. This agrees with the fact that hyposulphurous acid (11
2
22218 ) and sulphur appear at the cathode
,
the sulphur being pr need by the decomposition o f that acidform ed there in a concentrated state (Chem. News, Vol.XXXVI., p.Sulphurous acid in ueous solution is decomposed by the
current into .sulphur an sulphide of hydrogen, and sulphitesare gradually converted into sulphates. Thiosulphates areconverted into their correspond ing sulphates with separationof sulphur. The alkaline sulph ides
,according to their rich
ness in sulphur, are.decomposed with or without separation ofsulphur, sulphates bein formed. In the alkaline sulphatesand thiosul hates, in addition to sulphides
, polythionates areabrays prodhced (C. Luckow
,Jour.Chem.Soc.,Vol.XXXVIII.,
1 880, p. 283)
A copper zinc couple liberates sulphur from sulphurous acidwithout producing sulphuretted hydrogen (Gladstone andTribe, Jour. Chem. Soc., Vol. XXXIII., 1 87 8 , p.
Electrolysis of Sulph uric Acid . Molecularweig ht = 98 . Sulphuric anhydride (803) is a non-conductorwith a current from 14 Bunsen cells. Its solution in concen
5 1 4)
trated oil of V 1triol l s decomposed by a separate current w ithplatinum electrodes into oxygen at the anode and sulphur atthe cathode. By varying the proportion of the two substances ,part of the sulphur reduces the sulphuric acid to sulphuro usanhydride, which is evolved at the cathode (Geuther, Ann.Chem. et Pharm ,
Vol. CIX., p .. 130)By electrolysis
,concentrated English sulphuri c acid is de
composed with deposition of sulphur (C.‘Luckow
, J our.
Chem. Soc., Vol. XXXVIII., 1 880, p.
Separation ofPersulph uricAcid .-S. Berthelot divided
two portions of diluted and chilled sulphuric acid by a' porous
partition,immersed stout platinum wire electrodes l n the two
portions,and passed a dense current from three very large
Bunsen cells through the liquids, and thus obtained a mixtureof dilute sulphuric
o
acid containing 88 to 123 grammes of S2 70
per litre (Comptes Rendus, N0 VII. February 16th , 1880;Jour. Chem. Soc., Vol. XXXVIII., 1880, p.Liquid chloride of sulphur
,and also carbonic bisulphide
,are
non conductors.
Separation of Selenium — Se. Atomic weight = 7 9 5 . Acation
,acts also as an anion. Very little investigation has
yet been made of the electrolysis of compounds of this element.Amixture of aqueous hydrofluoric and selenic acids yieldedmuch red selenium upon the cathode. During the electrolysis by a separate current of an aqueous solution of selenateof nickel
,containing selenate of sodium and free selenic acid,
I repeatedly observed an abundant deposit of bright redselenium upon a platinum cathode. The deposition was nodoubt due to decomposition of the free acid , because it ceasedon neutralising the acid with ammonia. According to L.
Schicht (Chemisches Centralblatt, No. XXIV.,1880 also Berg
and Huttenmannische Z eitung , selenium is readily and
completely reduced and thrown down by a feeble current fromnot more than two cells
,both from acid and alkaline solutions
(Chem. News, Vol. XLl., p . 280, Vol. XLII., p. 331 , andEnglish Mechanic, Vol. XXXI ., p.
Separation of. Tellurium — Te. Atomic weight= l29. Atriad cation. Ritter
,and subsequently Sir H . Davy, observed
whilst electrolysing water with a tellurium cathode that thewater around the cathode acquired a purple colour by dissolving telluride of hydrogen
,and then precipitated a brown
powder. Magnus showed that the brown powder was metallictellurium set free by oxygen
,which diflused from the anode,
and decomposed the telluride. If the water is acid the telluride d oes not dissolve, but escapes as gas.L. Schicht states (ibid. that tellurium is readily and coni
pletely thrown down both from acid and alkaline solutions,
but more readily than selenium. From an acid solution it isE 2
52
easily‘
d eposited with a blue-black colour, and from alkalineones i t is separated in a very loose state at the anode withmuch evolution of gas, and if much metal is present it floatsas a light powder upon the liquid.Electrolysis of Telluric Fluoride and Chloride — I haveelectrolysed pure dilute hydrofluoric acid with an anode ofpure tellurium and a current from a single Smee element. Theaction was very slow, and most excellent deposits of brightreguline metal of grey colour and bright crystalline structurewere obtained. By electrolysing a pure solution of telluri cchloride by means of a very feeble current and large electrodesof smooth platinum I obtained only a j et black deposit
,chiefly
of non-adherent metal.For the electrolytic purification of tellurium,
see Watta’sD ictionary of Chemistry,
”Vol. VIII.,Part 2
,p.
Separation of Ph osph orus — P. Atomic weight = 31. A.triad element. Acts both as an anion and a cation. Accordsing to Burckhard (Chem. News, Vol. XXL , p. fusedpyrophosphate of sodium yields by electrolysis with a separatecurrent phosphorus and oxygen at the anode and soda at thecathode ; if the anode is composed of platinum a phosphide ofthat metal is formed.
Electrolysis of Oxid es of Ph osph orus — The electrolysis ofconcentrated phosphoric acid produces a metallic phosphi dewith the cathode when the latter is composed of copper or
platinum (H. Davy).By electrolysis with platinum electrodes dilute solutionsof phosphoric acid or phos
phates undergo no change (C.
Luckow,
'
Jour. Chem. Soc., V0 XXXVIII., 1880, p.The electrolysis of phosphoric acid and solutions of its s alts,
with electrodes of wood.charcoal or retort carbon
,produces .
phos
phamellogen , and with graphite electrodes phospho
g rap itic acid (Bartoli and Papasogli, Jour. Chem. Soc ,Vol.
XLIV.,1883
,p. 5 92; TheElectrician, Vol.XL, pp. 28 and
Chl orides, Bromid es, and Iodid es of Ph osph orus — Theseare non-conductors of a voltaic current.
Separation of Arsenic — As. Atomic weight = 75. A triadcation. Easily separated by various electrolytic processesPalladium charged with hydrogen reduces a solution ofarsenious acid to metal without producing arsenide of hydrogen (Glad stone and Tribe, Jour. Chem. Soc., Vol. XXXIII.,1878 , p. It is also separated- 1. By dissolving arseniousacid in warm dilute hydrochloric acid and stirring the solutionwith a piece of clean copper the latter acquires a coatingof arsenic ; this is the well known
“ Reinsch ’s test for theelement 2. By contact of zinc with platinum in solutions ofarsenic the latter is deposited upon the platinum ; and 3. Bypassing a separate current through a solution of arsenic in
( 53 )
d ilute hydrofluoric acid, by means of an anode of arsenic anda cathode of platinum
,I have obtained a scaly deposit of the
metal.The electrolysis of arsenic acid and solutions of its soluble
.s alts and electrodes of wood charcoal,or gas carbon, yields
mellogen free from arsenic (Bartoli and Papasog li, Jour.Chem. Soc., Vol. XLIV.
, 1883, p. 5 92 TheE lectrician,Vol.XL,
p p. 28 and
Separation of Arsen ide of Hydrog en.— AsH
3. Molecular
weight 7 8. From acid solutions of arsenic,magnesium by
s imple immersion evolves this poisonous and inflammablec ompound (Roussin, Chem. News. Vol. XIV.,
p. Marsh’st est for arsenic consists in evolving this g as from an acids olution of arsenic by simple immersion of zinc in it. Thes ame g as is evolved at a platinum cathode by the passage of aseparate current through solutions of arsenic, when the currentis sufficiently strong. A solid hydride of arsenic
,supposed to
have the composition As.H2,is produced when water is
electrolysed by a strong current, with metallic arsenic for thecathode Watts
’s“D ictionary of Chemistry,
”Vol. III.,p.
Terchloride of Arsenic.— As01
3. Molecular weight 18 15 .
This liquid is a non-conductor of a voltaic current,but the
aqueous solution conducts readily and is decomposed.For the electrolytic analysis of arsenic, see Jour. Chem. Soc.,
Vol. XLII., 1882, p. also Chem. News, Vol. XLVL,
p. 106. And for the detection of arsenic in mineral waters bymeans of a voltaic couple of tin and g old, see J. Lefort, Jour.Chem.Soc., Vol. XXXVIII., 1880, p. 5 10.Separation of An timony.— Sb. Elec. chem.eqt.
1
732
4000.
A triad cation. This metal may be obtained from its solut ions by all themethods of electrolysis. It is easily depositedfrom an acid solution of its . terchloride by simple contacto f various .metals. Z inc
,bismuth
,tin, lead, brass, and
German silver were coated with antimony by simple immersion in that solution ; but platinum,
gold, silver, nickel,and antimony were not. The simple immersion process isu sed to impart a lilac colour to articles of brass. A small
quantity of hydrochloric acid , which has been perfectly saturated with freshly precipitated and wet teroxide of antimony,‘
is precipitated by addition of a large bulk of water the
mixture is boiled until the precipitate is nearly re-dissolved ,more water is added
,and the mixture boiled again in like
manner,and then filtered. The clear liquid is heated to the
boiling point, and then perfectly clean articles of brass are
immersed in it. Th ey at once acquire a film of antimony and.a lilac colour, and, by allowing them to remain a greater orless length of tint s of colour are obtained.
( 54 )
I have observed that z 1nc readily deposits antimony as a
black powder by simple immersion in an aqueous solution ofthe mixed fluorides of antimony and potassium
,that copper
also deposits it as a black film and powder by contact with theacid hydrochlorate of terchloride of antimony
,and that
crystals of silicon did not become coated with antimony in anaqueous solution of terfluoride of antimony containing freehydrofluoric acid ; also, that the oxide of iron upon a rustyiron wire was rapidly dissolved in a mix ture of equal measuresof solution of terchlorid e of antimony, and a saturated so lu7,tion of sal-ammoniac. \Vatt coats copper with antimony by
,
irrimersing it during about half an hour in a solution of one,
ounce of chloride of antimony, one pint of spirit of wine, with,suffi cient hydrochloric acid ad ded to make the mixture clear.I have noticed that antimony is deposited by simple immersion from its ordinary chloride, as prepared for pharmaceu
tical purposes by zinc, bismuth, tin , lead , brass, and Germansilver, but not by antimony, nickel , silver, gold , or platinum.
According to Raoult, magnesium sets free antimoniurettedhydrogen
,but no metallic antimony from solutions of the
metal (Chem.News, Vol. XIV., p. Gold,in contact with
an timony, in a cold 01 hot solution of a salt of that metal, doesnot acquire a metallic coating (ibid .
,Vol. XL
,p.
The electrolysis of antimonic acid and solutions of its saltsWith electrodes of wood charcoal
,or retort carbon
,yields
stibiemellogen , and with raphite electrodes stibio- rag bitieacid (Bartoli and Papasogli, Jour. Chem. Soc., Vol. IV.,1883, p. 5 92 ; The Electrician, Vol. XI. p, p. 28 andA very good solution for obtaining the pure metal by the
separate current process, with an anode of antimony, is com
posed ofParts by weighu
D istilled waterPure hydrochloric acidTartari c acidPotas sio tartrate of an timony
The electric current shou ld be from about two Smeeelements, quite feeble, and of such a strength as to deposi t athickness of metal no t exceed ing 3
r
ejnd of an inch per week.
The metal thus deposited is hard , close grained , of a slaterey colour
, silky lustre,and of decided crystalline structure,
During deposition , when it has attained a thickness ofTl
3 th
of an inch,it sometimes cracks spontaneous ly, and becomes
curved in fantastic shapes, or if deposited on a thin metalcathode it causes the latter to bend.
Electrolysis of Teroxide of Antimony.— Sb03. Molecular
Weight a 16‘8 Th is compound; in a fused state, is reduc ed to
metal by contact with charcoal.
( 5 5 1
Electrolysis of Terfluorid e ofAntimony — SbF3: Molecular
weight = 17 7 . This is 'a very soluble salt
, and,3
unlike thechloride, is not at all decomposed by the addition to it of alarge quantity of water. ‘ By electrolysis with a separatecurrent of suitable strength , and an anode of antimony, itslowly yields a thick layer of thepure hard grey metal.By employing a dilute solution of the fluorid e containing
fre‘e hydrofluoric acid , and using a current from two Smeecells
,or by passing a
- current from ten such cells through asaturated neutral solution of the fluoride,during a long periodof time, I -have obtained very beautiful collections of shininggrey crystals of the metal, which do not oxidise by exposure
Electrolysis of TerchlorideofAn timony — SbCl3.Molecular
weight = 226 5. Froma solution of this salt containing freehydrochloric acid, the antimony may be obtained by theseparate current process
,and an antimony anode, either in the
form of the pure grey metal , or in that known as amorphous”Br explosive”antimony, according to the degree of density ofth e current and the composition and temperature of the liquidThe acidified aqueous solution of chloride of antimony is an
excellent conductor of the current , it dissolves an antimonyanode freely, yields plenty of the amorphous metal , and doesnot deteriorate by use or by exposure to the atmosphere. Itis,however
,decomposed with greater or less rapidity by con
tact with zinc,cadmium
,tin
,lead
,iron
,brass
,copper and
German silver,each of which deposits the metal upon itself
and dissolves. It 1s also decomposed by water, and therefo rearticles wet with water must not be immersed m it, and thesetaken from the liquid must be washed with dilute hydrochloric acid or a solution of tartaric acid previous to washingthem with water.
Explosive Antimony. -To obtain the explosive varietyof metal from the usual acidified solution , the current sh ouldbe o f such a strength as to deposit not less than half a grainofm etal per square inch of cathode per hour. If the streng thismuch less
,the kind of deposit suddenly changes to the grey
variety, sometimes preceded by formation of nodules of that
kind upon parts of the surface of the cathode. The two kindso f deposit do not adhere firmly to each' other.A good solution for yield ing the explosive variety is
composed of one ounce of freshly precipitated teroxide 'or
oxychloride of antimony,dissolved 1n five or six ounces of pure
hydrochloric acid of specific gravity 1 12,or it may be madeby
saturating two volumes of the acid with the oxide or oxychloride , and then adding one additional volume of the acid.The
‘
oxideemployed should not be that which ’ has been madeby oxidising {antimonywith nitric"acid
, or' with any mixture
( 56 )
containing that acid,nor should it be that which has long been
exposed to the air. A good solution may also be made bymixing together two ounces of water, four of hydrochloricacid
,and eight of finely powdered potassio tartrate of antimonytartar emetic). Either of these mixtures will bear a very
strong electric current without causing the deposition of ablack powder. It yields its metal rapidly, and coatings of anydesired thickness may be obtained . I have had some of quiteh alf an inch in thickness. Deposits of one-tenth of an inchthick may be obtained from it in about seventy hours bymeans of a current from two or three Smee elements.A suitable depositin liquid may also be prepared by the
“battery process,”i.e., y immersing a large anode of antimony
and a smaller cathod e of platinum, silver, or copper in thedilute acid
,and passing a cepious current until the metal is
freely deposited.The explosive variety of do it has quite a different appear
ance from that of the other. t is highly smooth and lustrous,and of a steel-black colour. Its appearance, however, variessomewhat with the speed of deposit mn. It has the remarkableproperty that if struck, broken, or rubbed, whilst at the
ordinary temperature, or if touched with a. red -hot wire,it
suddenly rises in temperature, usually about G5O°
F. the
amount of heat, however, vari es with different circumstances.Another difference between the ure variety of metal and theexplosive kind is that, when eposited upon a cathode ofmercury, the former is absorbed by and alloys with themercury,but the latter does not.Like most electro-deposited metals, and especially the pure
variety of an timony, the outer and inner surfaces of deposi tsof the explosive kind are in states of different cohesive strain
,
wh ich sometimes cause the deposit to crack spontaneously inthe deposi ting liquid and shatter to bits , evolving all its heat.Faint crackling sounds not unfrequently issue from bothvarieties of the deposi ting metals whilst forming in the liquids.Sometimes, with a very dense solution of the ch loride,
worked rapidly, and the liquid and cathode not at all
disturbed , a layer of deposited metal , in the shape of a largebutton 11 inch diameter, gradually formed round the cathode,just at the surface of the liquid.A cylindrical bar of the explosive variety, about gths of an
inch in diameter, formed upon a rod of tin 1th of an inchthick, when discharged by momentary contact of a heatedwire
,instantly evolved sufficient heat to melt the tin com
pletely, and the tin ran out and remained liquid a short time.The change which takes place is propagated from particle toparticle of the mass. By forming depos its of sufficient thickness upon helices of stout copper wire, and discharging themby application of heat to one end, the change was gradually
( 58 )
1’ It appears, therefore, that thedeposit 18 a species b f chemicalcompound of the metal with the ingredients of the liquid ; andthat d uring the change its state of chemical union is destroyed.R. Biittger has stated (Chemisches Central Blalt, 1875 , p. 674)that the freshly deposited active metal contains occludedhydrogen ,
but this has been contradicted.Smee appears to have been the first to deposit this variety of
antimony,but not to notice its singular property but since I'
first observed it in October, ' 1854,several persons have red isJ
covered it (see Comp tes Rendns, Vol. LXXXIIL pp. 854— 85 7 ;also Dingl. Poly. Jenn ,
Vol. 207, p. 427 , and Jonr. Chem. Soc.,XL, p.solution composed of the double chloride of antimony and
ammonium,with free hydrochloric acid
,may be used instead
cf that of the acidulated simple chloride for depositing themetal
,but po ssessess no very great advantages.
Electrolysis of Terbromide of An timony -. ShBr3. Moles
onlar weight == 360. The electrolytic properties of a solution ofthis salt are much like those of the chloride. It, however, lessreadily yields a fi rm deposit of metal. Asecond variety of theactive
,
substance was obtained from i t in the followingman nerzs-L-Dissolve one part by '
weig ht of freshly-made teroxideef an timon y in ’ ten ‘ parts of aqueous hydrobromic acid of
specific gravity about 10. Filter the solution and electrolysei t with an -anode of antimony and a current from three Smee
'
cells, at a speed of deposition of about 4 grains of metal persquare inch of cathode per hour.b The xd epomts thus obtained were of a. l ighter colour thanthose from the chloride, they were also quite dull in aspectsand frequentlyperforated with holes all over the surface like asponge. This was caus ed by numerous bubbles of gas. The
’
deposi t is'
less,
apt to spontaneously crack than the first variety ;it 18 also much more fragile and less hard . Its specific gravi tyat 60
°
F. is also much lass, and varies from 5 415 to 5 472.
It contains a less percentage , viz., 7 9 52, of metallic antimony.The residue consists of a colourless soft substance composed of ‘
terbremide of the metal, and —a little hydrobromic acid andwater.It exhibited the sam e kind of thermic action as the first ‘
kind , but the change did not spread throughout the mass“
unless the substance was previously heated to about 25O°
F.
By contact with a red hot wire it then evolved all its heat '
instantly with explosive violence,and with fracture and
dispersion of the substance. By gradually heating the entiresubstance to about 320
"
E i t exploded suddenly.In two pairs of’ experiments made to ascertain the electrochemical equivalen t of this deposit I obtained 5009 and 501 1 ,also 5 12 and “5114 parts for eyery 425 parts of the active
chloride variety deposited , or 32°2 parts of z inc consumed;m
the same circuit. Each of the quantities of the two kinds ofdeposi t contained about the same
,viz., 40parts, 101 .
—rd of an
atomic weight of metallic antimony,the remainder being the
associated salt of the metal. These results indicate that ineach case the metal alon e 1s d eposited by the current
, and thatduring the act of deposition it occludes the saline .matter
,and
acquires the peculiar property.
Electrolysis of Teriod ide of An timony —.Sbl Molecular
weight 503. The solution ' employed was pres
pared as fol!lows f— D issolve one part by weight of recently precipi tatedteroxide of antimony in fifteen p arts of aqueous hydriod icacid of specific gravity 1
°25 . A current sufficiently strong waspassed through it
,by means of an anode of antimony, to
deposit the metal at a rate not exceeding one grain weight per.square inch of cathode per hour. During the process the
tendency to evolution of hydrogen was so great as frequentlyto completelydisintegrate the deposi t. 1
The substance thus obtained was dull m appearance, grey incolour, scaly, extremely fragile, soft
,and much less metallm
than even that obtained in the hromide solution. Its specificgravi ty was 5 27. On immersing it in water bubbles of g asissued from all parts of its surface during a few seconds, andproduced a hissing sound like that of slaking lime. Piecesone n inth of an inch in thickness required to be heated to338
°
F. before the contact of a red hot W 1rewould cause themto d ischarg e their heat ; they then discharged feebly andevolved red vapours of antimonic iodide .Theunchanged substance yielded on analysis 77
°76 per cent.of metal
,the remainder being solid red iodide of antimony
and a little aqueous hydriodic acid . By deposi ting it slowly,1 .e.
,at the rate of °5 grain per square inch of cathode perhour,
in the same circuit as the chloride variety, its electro chemicalequivalent was determined , arid 48 07 parts were obtained forevery 42
°5 parts of the other kind. The deficiency of equivalen t of metal consisted
,no doubt, of deposited hydrogen.
For a more complete account of the several varieti es ofelectro deposited antimony from the three salts seePhil. Trans.Roy Soc., 185 7 , 18 58 , and 1862; also Chem. News
, Vol. VIII.,pp. 257 and 28 1 ; and Jonr. Chem. Soc.
Electrolysis of Tersulphide of Antimony.L— Sn . Moleonlar weight = 218. This compound when in a fused state isread ily decomposed
,and the antimony separated by
coal,and various metals
,e.g ., potassium; sodium, copper, tin,
iron,&c
n Electrolysis of Ch lorides of Arsenic and An timony. —In
the electrolysis of thechlorides of arsenic and antia'
y seine
a rsenide and antimonide 1 of~ hydrogenJere 1 1produced fatwthe
( 60 >
c athode. If the three metals — arsenic,antimony
,and tin-J
are simultaneously resent they are deposited in the order
g iven. From the so ution s of the sulphides of those metalsin alkaline sulphides tin and antimony are deposited com
pletely, and arsenic not quite comple tely, in the metallic stateJour. Chem.Soc., Vol. XXXVIII., 1880, p.
Electrolysis of Antimoniate of Potassium.— Bartoli and
Papasogli electrolysed an aqueous solution of this salt bym eans of a current from eight Bunsen cells and an anode ofw ood charcoal or gas carbon. Very much gas was evolved atthe cathod e , and a small amount at the anode. The anode wass trongly attacked, and the electrolyte became deep black. Theauthors found in the electrolyte a compound of carbon, hydro
g en ,oxygen, and antimony, which they term stibiomellogen
(Jour. Chem. Soc., Vol. XLII., 1882, p.For the electro-chemical analys is of antimony compounds
see q r. Chem. Soc., Vol. XLII., 1882, p. Chem.News,Vol. XLVI., p. 106.
Separation of Bismuth — Bi. Atomic weight 210. Atriad cation. Much less easily deposited in a coherent statethan antimony. By simple immersion tin coats itself withvery small shining plates of bismuth in a solution of ten grainso f nitrate of bismuth and a wineglassful of distilled water, towhich two drops of nitric acid have been added. Commaille
(Chem.News, Vol. XIV., p. 188) states that magnesium depo
s its bismuth from solutions of its salts by simple immersion.I have observed that it is also do sited from its aqueouschloride by zinc, tin, lead and iron, ut not by bismuth
,anti
m ony, copper, brass , German silver, gold, or platinum.
Electrolysis of Oxide of Bismuth — Burckhard states thatfused oxide of bismuth is easily decomposed by a current fromtwelve Bunsen cells with electrodes of copper ; i f platinumw ires are used , an easily fusible alloy of the two metals isformed (Z eitschm
’
ftf iér Chemie, Vol. VL, p. Melted oxideof bismuth is instantly reduced to meta l by contact with antimony (H. Tamm,
Chem.News, Vol. XXV., pp. 85
Formation of Peroxide of Bismuth .— Wernicke has pre
pared this compound as a black deposit, having the compositionrepresented by B10”H20, and a specific gravi ty of 5 5 7 1, byelectrolysing by a current from two Daniell cells, with ananod e and cathode of sheet platinum, a solution of a mixtureof basic nitrate of bismuth and tartrate of sodium (Pogg .
,Annalen, Vol. CXLI., p.
Electrolysis of Nitrate of Bismuth — Sodium amalgam1 d ecomposes a saturated solution of nitrate o f bismuth, settingfree hydrogen and black powder of bismuth (Bottger). Bythe
,
separate current , process an anode‘
of the metal,an ex
( 61 )
tremely feeble current, and a solution of the nitrate in water,wi th the minimum amount of free acid
,to render it clear
,11
have deposited the‘
metal as a very beautiful but thin coating,
white, with a faintly pinkish tint, and a fine silky lustree
According to some writers 8 10h a deposit is explosive.
Electrolysis of Fluoride of Bismuth — With pure dilutehydrofluoric acid
,a bismuth anode
,and a current from a single
Smee element, the conduction was extremely feeble, and onlya black film was deposited upon a copper cathode in thirtyhours.
Electrolysis of Ch loride and Iod ide o'
f Bismuth — Metallicbismuth may be deposited upon copper or brass, by means,
or
a current , from a single Bun sen cell, from a solution composedof 25 to 30 grammes of the double chloride of bismuth and.ammonium ,
d issolved in a litre of water,faintly acidified with.
hydrochloric acid. The deposit consists of a blackish mud ,with a film of bright adherent bismuth beneath (Bertrand,Athemeum,
April 22, 1 876, p. 5 70 also Jour. Chem. Soc.,Vol. I., 1 8 7 6, p. I have deposited the metal
,evidently
containing some ingredients of the liquid,by a separate cur !
rent and a bismuth anode,from a solution of iodide of bismuth
and iodide of potassium. The deposit was an extremely bulkyjet black powder
,which contained iodine even after most per
sistent washing, and became slowly oxidised by exposure tothe atmosphere.A cyanide solution has also been recommended for d epositing
bismuth, but an anode of that metal does not readily dissolvein a hot solution of potassic cyanide.One part of bismuth in parts of mercury may be
detected by the addition of potassium amalgam and water, thebismuth being electrolytically separated as a black powder onthe sides of the vessel (Serullas, Ann .Chem.etPhys ,
3rd Series,
Vol. XXXIV.,p.
For the electrolyti c analysis of compounds of bismuth see
V.Francken , Chem.News,Vol.XLVI., p. 106 also Jour..Chem.
Soc.,Vol. XLII., 1882, pp. 8 96 and
Separation of Osmium — Os. Atomic weight = 1 99. Acation. Z inc deposits osmium in the form of black
'
fiocks
when immersed in a solution of the black oxide in coneentrated hydrochloric acid. Metallic mercury decomposes a
solution of osmic acid, and forms an amalgam of osmium and}mercury (Tennant).Smee electrolysed a solution of osmic acid (OsO4), and ob
tained a black deposit. Wohler passed a current from two
Bunsen cells by means of an anode of osmium through dilutesulphuric acid ; the metal was freely converted in to osmie
acid also through a solution ofc austic soda the ' latter became
( 03 )
of a deepyellow colour, and a deposi t of osmium was formedupon the cathode (Chem. News, Vol. XIX.
,p.
Ruth enium.— E u. Atomic weight A cation. Noreliable electrolytic experiments appear to have been madewith thismetal. Its great rarity and infusibility
,extreme
cost,
'
aud porous structure,are the chief obstacles.
Separation of Rhodium — R0. Atomic weight = 104 °3. Acation. Smee stated that by means of a separate current fromten of his cells
,and platinum electrodes
,he deposited this
metal from a solution of its sodic-chloride,and obtained a
brittle white deposit ; and that with a stronger current thed eposit was a black powder.
Separation of Iridium.— Ir. Atomic weight = 1 97.Acation .
Sodium amalgam decomposes a concentrated solution of sod io~iridium chloride, and forms an amal am of iridium. Accord ingto F.Wohler
,osmi-iridium rs readi1 y dissolved as an an ode 1 11
a solution of caustic soda. Smee stated that he had depositedthis metal in a bright reguline state on a smal l scale. According to a writer in Pingler
’
s Polytechnick Journal, both electrod eposited i ridium and rhodium detonate when heated (Jour.Chem. Soc., 2nd Series, Vol. XL , p. probably in conse
quenco of their containing hydrogen.
Separation of Pallad ium — Pd. Atomi c weight= 1005 . Acation. Mercury decomposes a solution of a palladium salt
,
and forms an amalgam. According to S. Kern (Chem. News,
Vol.XXXIII.,p. the immersion of magnesium in aqueous
solutions of salts of palladium yields hydrogen,monoxide of
pallad ium,and hydrogenated palladium.
Formation of Peroxide of Pallad ium.— Pd0
2. Molecular
weight = 158 °5 . An anode of palladium , used to conduct acurrent from two Bunsen elements into dilute sulphuric acid,became slowly covered wi th an almost insoluble film of thisc ompound (F. \V6hler, Chem. News, Vol. XIX.
, p.I passed a current from fifty Smee elements, by means of a
palladium anode and platinum cathode, through dilute sul
phuric acid. No odour of ozone occurred at the anode, unlessthe latter dipped but a very small depth into the liquid. Con
d uction was copious,and a deposit of splendid colour— red ,
purple,&c.— formed upon the anode. By reversing the direc
tion of the current the now well-known phenomenon of bending of the cathode by absorption of hydrogen took place ; andby removing the charged cathode from the liquid and bendingit by mechanical means it evolved heat.
Electrolysis of Nitrate of Palladium — A solution of thissalt is said to be a good conductor
,but apt to yield the metal
in .the form of a black powder. I electrolysed strong n itric
acid, b y means of a current from fifty Sme‘e cells, .with -‘
a
palladium anode and platinum cathode. Cupious conduction ,and rapid decomposition of the acid, with abundant evolutionof red fumes, took place. Much g as was set free from theanode, but n one from the cathode until atter a short time. Theanode was not at first visibly corroded , but after half an hour
’
s
a ction the palladium slowly dissolved,forming a red liquid.
No metallic deposit formed upon the cathode.Nitrate of palladium dissolved in water and acidified with a
‘little nitri c acid, deposited upon the cathode .a bronze colouredc oating, which by prolonged action became darker, and thenblack
,and was easily soluble in nitri c acid. Some reddish
oxidewas formed upon the anode. Alkaline solutions behaveds imilarly, except that the action was slower, and the depositedm etal more adhesive (Schucht. Berg ilud
' HuttenmannischeZ eitung
,Chem.News, Vol. XLI., p.
Formation p f Fluorid e of Palladium.— PdF
4. Molecular
weight = 182°5. I electrolysed thirty per cent. pure aqueoushydrofluoric acid
,with a sheet palladium anode
,in a large
p latinum vessel as the cathode, by -means‘
of a current froms ix Smee elements. Free conduction occurred
,and much gas
w as“evolved from each electrode
,and there was a strong odour
o f ozone. A dark,red-brown
,thin coating for medupon the
palladium,but did not dissolve during fifteen hours’ electro~
lysis. .The liquid was filled with minute floating particles ofpalladium
,caused by the reducing action of the hydrogen from
t he cathode. After six days’ continuous action the anode was
g reatly corroded.I also electrolysed
'
the pure anhydrous acid in a chilled state,in the same vessel
,with a thick palladium anode and the same
current, and sometimes with a current from thirty cells. The
p rocess was diflicult and very dangerous, and notwi thstandingt he low temperature, and that the vessel was closely coveredby a lid of paraffin
,the acid volatilised rapidly and fumed
greatly,partly in consequence of the escaping hydrogen and
the heat of conduction resistance. The coldness of the vesseland the intense attraction of the acid for moisture causedwater to condense upon the lid of the vessel , and rendered itd ifficult to preserve the acid in the anhydrous state. Thelid was therefore made to overhang the edge of the cup, andwas also covered by a layer of cotton wool. With a currentfrom twenty cells the conduction was copious. The anode
quickly became coated with a thick, dark, red-brown, brittlec rust
,which was of a redder colour on the side next the anode,
and did not perceptibly impede the passage of the current.This crust was scraped off at intervals of about one hour intoa platinum dish standing upon a slab of iron heated to about350
°
F.,and at once transferred to a closed platinum bottle.
K“ )
After eleven~ hours’ action, the acid was still colourless, as if
the crust upon the anode was perfectly insoluble.~ Some blackpowder
,which proved to be metallic palladium
,was
,however
,
found upon the cathode, and indicated that some palladiumhad dissolved and been reduced. The crust also on the sidetowards the anode was nearly black when dry, and showedsigns of metallic particles when pressed between smoothsurfaces of agate, indicating some reduction by the diffusedhydrogen.In some other experiments the hydrogen wasmore perfectly
excluded from touching the anode. The platinum cup was22 inches wid e and 3} inch es deep, divided into two equalparts by a well-fitting vertical plate of paraffin, which extendedto within half an inch of the bottom. The palladium anodeand platinum cathod e were each about 4 inches long and1 inch wide
,and firmly fixed in slits in the two halves of the
paraffin lid. With 5} ounces of the perfectly anhydrous acid ,and a current from twelve one pint Grove cells
,the conduction
was copious, and in five minutes the immersed part of theanode had acqu ired a deep brown colour. The electrolysiswas continued during five hours, the anode being taken outand scraped each half hour
,and the crust preserved in a
platinum bottle. The crust was hard , and sparks were somet imes caused by particles of i t being decomposed by the heatof friction in removing it. A hiss ing sound was heard duringthe whole of the electrolysis, but the densi ty of the fumesprevented any effervescence being seen. grains of blackpowder were found upon the cathod e and adjacent parts of thevessel and partition
,and yielded 101 1 grains of metallic
palladium,this indicated some small degree of solubility of
the crust, and the great necessity of excluding hydrogen fromtouching the anode. The anode had lost grains inweight
,and 54 °13 grains of the dry brown crust was obtained .
After deducting the 101 1 grains of palladium found in theliquid
,the remaining quantity of corroded metal would form
only 47 62grains of tetrafiuoride ; the crust therefore containedin addition probably some hydrofluoric acid.I also found that a palladium anode was very rapidly cor
rod ed by the passage of a current from six Grove elementsthrough pure potassic fluoride in a state of fusion. Finelydivided palladium was found in the saline residue.
Electrolysis of Ch loride and Iod ide of Palladium — I
electrolysed concentrated,also dilute hydrochloric acid
,by a
current from fifty Smee cells with a palladium anode and a
platinum cathode. Action was instant and rapid,hydrogen
was copiously evolved from the cathode and chlorine from theanode ,
“
and the anode dissolved,forming a blood-red liquid, and
a black deposit of palladium soon formed upon the cathode.
t 5 6 l
silver in a solution of tetrachloride of platinum,they became
coated with that metal. According to Lan ,a solution of one?
part of platinic chloride in 15 parts of alcohol and 50of etherdeposits platinum on tin
,brass
,and white metal (Jour. Chem .
Soc., Vol. XLII., 1882, p. B'
ottger adds carbonate ofsodium to platinic chloride as long as carbonic anhydride isevolved , then a little starch sugar
,and
,finally
,chloride of
sodium till the precipitated platinum appears white. Theresulting solution coats articles by simple immersion (Watts
’
s
“ D ictionary of Chemistry,
”Vol. VI., p.One of the best liquids for obtaining thick regul ine deposits
by the separate current process is that of Roseleur, who prepared it as follows z— Convert 10 parts of platinum into drytetrachloride, and dissolve i t in 500 parts of distilled water
(the whole should d issolve). Add , with stirring,to the solu
tion 100parts of crystallised phosphate of ammonia previouslydissolved in 500parts of distilled water ; and as this producesa precipitate, add at once, with copious stirring, a ready-madesolution of 500parts of crystalline phosphate of soda inparts of distilled water. Boil the mixture until an odour ofammonia ceases and the liquid begins to turn blue litmuspaper red. The liquid must be used hot, an d a strong current must be employed
,because an anode of platinum does
not dissolve in it. It is decomposed by, and deposits platinumupon , zinc, tin , or lead by simple contact. A solution madeby dissolving tetrachloride of platinum i n one of potassi ccyanide has also been used for the same purpose, but it alsodoes not dissolve a platinum anode.
Formation of Tetrafluoride of Platinum — In some ex
periments,
of mine a platinum anod e in water, containing 10per cent. of pure anhydrous hydrofluoric acid , was not corrodedby the passage of a current from six Smee or six Groveelements during many hours. Very free conduction occurred;apowerful odour of ozone and a gas which inflamed a red -hot
sp int were evolved at the anod e, but no platinum was deposited. With an aqueous solution of pure potassic fluo rideprecisely similar effects occurred.A curren t from 24 elements of magn esium and platinum in
an exciting solution of - common salt was passed during 18
hours, by means ~of platinum electrodes, through water containing 40per cent. of the same pure acid, but no corrosion ofthe anode took place. With a current from ten Smee ‘
cells
and platinum electrodes I also electrolysed water contain ing80 per cent. of the pure acid. Abundant conduction withevolution of hydrogen and Ozone occurred ; the anod e lost
grains by corrosion during 36 hours, and became coveredwith a brownish black crust, which partly dissolved in theliquid to a brownish solution. No platinum was deposited ,
67
probably because the hydrogen decomposed the solution. Ialso electrolysed with platinum electrodes the pure anhydrousacid in a precisely similar way to that described under“ Fluoride of Palladium.
”With a current from forty Smeecells the anode corroded ~
rapidly, and acquired a dark redbrown crust, which was insoluble in the acid ,
'
but rapidlydeliquesced in the ai r ; i t d issolved , ,
with partial decomposi~tion, to a vbasic salt and formation of a blood-red liquid
,in
vvater.
By electrolysiswith platinum electrodes,during 16
'
hours,
of water containing 40 per cent. of the pure acid,mixed with
its own bulk of strong nitric acid , gases were freely evolved ;but scarcely any platinum was dissolved
,and none was de
posited. With an equal bulk of strong hydrochloric acidsubstituted for the nitric
,hydrogen and chlorine were set
free,but in four hours’ action the anode was very little
corroded. With the same volume of sulphuric instead of the.
nitric acid,after many hours’ action
,the anode was again but
little corroded. With phosphoric anhydride dissolved indilute hydrofluoric acid
,and the mixture electrolysed , the .
results were similar. And with much selenious acid dissolvedin it, selenium containing traces of platinum was freely deposited , and gas was evolved as before (see Phil. Trans. RoySoc., 1869, p.By electrolysing fused fluoride of potassium or lithium withplatinum electrodes
,the anode was rapidly dissolved, and the
resulting salt of platinum instantly d ecomposed , and its metalset free ; and by electrolysing pure double fluoride of hydrogenand potassium in a fused condition, the platinum anodewasrapidly dissolved
,and a colour imparted to the sal t. Fused
silico—fluoride of potassium,or the fused fluorides of si lver,
copper,lead
,manganese
,or uranium,
when electrolysed by .
a current from six Smee cells, did not corrode a platinumanode.
Electrolysis of Tetrach loride of Platinum. Pt. 014.
Molecular weight = 339. This salt may be formed by theelectrolysis of hydrochlori c acid with a platinum anode andense current. According to Commaille (Chem. News, Vol.XIV.,
p. 188) magn esium deposits pure platinum from a solution of platinic chloride. I have observed that crystals of'
silicon did not acquire a coating of platinum in °that liquid .
A smooth deposit of platinum upon bright copper ‘
may beobtained by immersing the copper -in° a boiling solution com
posed of 100parts of distilled water, 12 of caustic soda (or 40of sodic 10of platinic chloride. Copper aridbrass may also be coated by means of contact with zinc in asolution prepared as follows -To a solution of platinic chlorideadd sodic carbonate in fine powder until efl
'
ervescen cé ceases,F 2
( 08 )
then add some glucose, and afterwards as much sodic chlorideas will produce a white precipitate. The solution should beused at a temperature of 60
°
C. Les Mondes,
”Chem.News,
Vol.
Separation of Gold — Au. Atomic weight = 1966 . A triadcation. Like platinum, gold is very easily separated from itssolutions by each of the methods of electrolysis. Thalliumdeposits go ld from its solutions (W. C.Reid , Chem.News, Vol.XII.
,p. Auric terchloride and the euro-cyan ide of
potassium are the only common soluble salts of the metal ; asolution of the oxide in hydrobromic acid, or of the aurateof ammonia (a very explosive substance) in potassic cyanidepreviously dissolved in water, may also be employed. A goldanode is corroded and dissolved in various liquids, e.g ., hydrochloric acid
,solution of sodic chloride, &c. Runspaden has
observed that a gold anode in dilute sul huric acid is considerably oxidised , and a definite hyd rat oxide of gold isformed (Chem. News
,Vol. XX.
,p. By immersing zinc
in a solution of sulphide of gold dissolved in one of sulphideof ammonium,
excluded from the atmosphere,i t becomes
coated with gold (0. D. Braun, Chem. News, Vol. XXIX.,
pJ. Schiel has produced Nobili’s rings on a horizontal plate ofburnished gold used as the anode in very dilute nitric acid
,the
negative pole being a platinum wire, supported a short distanceabove the gold plate. After passing a current of suitables treng th during about ten minutes, the plate was washed,d ried
,and exposed a few hours to sunlight ; the rings then
appeared of brilliant colours. With an alkaline solution theeffects were less powerful (Pogg.Ann . CLIX., p.Under the influence of an electri c current nitri c acid dis
solves gold (Berthelot, Jour. Chem.Soc., Vol. XXXVIII., 1880,p. 158)Formation of Fluoride of Gold — By elec trolysing pure
dilute hydrofluoric acid with a gold anode,in a platinum
crucible as the cathode, bymeans of a current from six Smeecells
,during many hours , the current passed very freely, much
g as came from each electrode, and an odour of ozone from theanode. The anode gradually became covered with an insolublered -brown film. None of the metal d issolved. Similar effectsoccurred w ith more concentrated acid, and with a very muchstronger current. The red-brown film appeared to be gold ;it was insoluble in nitric acid, and when burnished with agateit appeared like gold.With a gold anode in pure anhydrous hydrofluoric acid, at
10°
F.,even a current from forty Smee cells was but feebly
transmitted. In one and a-half hour the anode acquired adark
,reddish-brown film, with a few crystals
,at first of a
( 69 )
greenish colour, upon its edges. By exposure to the air thecrystals became fi rst yellow and then red. A current fromsix Smee cells was conducted freely by a gold anode
,in a
solution of pure fluoride of ammonium containing free ammonia.The anode evolved much gas, and became covered with an
insoluble, bright, lemon-coloured powder, but no gold appearedon the cathode. By means of a current from three and alsofrom six Grove elements I electrolysed with a gold anode thepure fluorides of potassium and lithium in a melted state.Metallic gold separated, and the anode was very rapidlycorroded.
Electrolysis of Auric Terch loride.— Au.013. Molecular
weight = 303 °1. Sodium amalgam easily reduces a solutionof auric terchloride, and , according to G.A Koenig, ev
'
en charcoal reduces it to metal by simple immersion (Journal of theFranklin Institute
,May
, 1882 see also Chem. News, Vol .
XLIV., p. The mere contact of magnesium, phosphorus,arsenic
,antimony
,tellurium
,bismuth
,palladium
,silver,
mercury, copper, and nearly all the base and brittle metals,with this solution separates the metal. I have noticed thatcrystals of silicon did not reduce it, but that by contact ofamylene
,
“ petroleum ether,
”benzine,coal gas, and numerous
liquid hydrocarbons,with the aqueous solution, films of the
1
1
1
3
1etal gradually separated (seePros. Birm. Phil. Soc., Vol. IV.,
art I.Accdrding to D. Tommasi, solution of auric chloride is notreduced to metal by hydrogen or platinum alone, but only byhydrogen in the presence of platinum (Chem.News, Vol.XLI.,p. 1 16)
Electrolysis of Aura-Cyanide of Potassium.— K0y.AuCy .
Molecular weight = 287 °7 In a solution of the double cyanideof gold and potassium
,zinc
,copper, brass, and German silver,
became gilded by simple immersion ; but platinum, gold, silver,nickel
,iron
,lead
,tin
,bismuth, and antimony did not.
This salt,when dissolved in asuitable preportion of water,
and a certain preportion of potassic cyanide added, constitutesthe ordinary . electro-gilding solution. The compound mayeither be formed by dissolving the salts in water, or by tah 1nga solution of potassic cyanide, and electrolysing it wrth ananode of gold and a cathode of platinum, until gold 1s freelydeposited. This process
,however
,leaves a large excess
.
ofsimple potassic cyanide in the liquid, and also by abstractingsome of the cyanogen to form auric cyanide, and subst1tut1ngoxygen in its stead, i t introduces caustic potash , and thecaustic alkali gradually becomes carbonate by absorbing car
bonic acid from the atmosphere. The solution , when formed ,
yields by electrolysis gold at the cathode, whilst cyanide ofgold is formed at the anode, and dissolves.
For deposition of gold by an electric current in solution 1 of
potassic ferrocyanide and auric chloride , seeE. Ebermayer,Joar. Chem. Soc., Vol. XXXIV.
,1 87 8 , p. 1 7 8. For a solution
suitable for gilding iron, seeWatts’
s“D ictionary of Chemistry,
”Vol. VIII., Part II., p. A g reat variety of mixtures,containing auri c chloride or cyanide, and other substances,such as the carbonates and chlorides of potassium and sodium,
sodic bisulphate , phosphate, and pe phosphate, potassic ferrecyanide
,and sulphocyanide, aqueous ammonia, carbonate of
ammonium,&c., have been employed for electro-gilding. The
particulars of their composition may be found in“ The Art
of Electro-Metallurgy,”Longmans and Co.
’
8 Text Books ofScience.”By electrolysing a solution of methylamine with a goldanode and a feeble current during several days I obtained nodeposit of gold.
Separation of Silver. -Ag . Atomic weight 108 .A
monad cation. Its commonest soluble salts are the,
nitrate,acetate
,argento-potassic cyanide, ammonic-nitrate, and em
mon io chloride. Other soluble ones are ammonic carbonate,sod ic hyposulphite, argento-potassic iodide , potassio-tartrate,and argento-potassic sulphocyanide. Sulphate of silver is butslight ly soluble. All the solutions of silver are readily decemposed by an electric current with deposition of metal upon thecathode
,and in some cases with oxidation of the silver of the
liquid at the anod e, an d formation of argentic peroxide.Nearly all the solutions of the salts of silver are reduced tometal by simple immersion in them ,
oi any of the base metals.Aluminium reduces the silver from an ammoniacal solution ofargentic chromate (Watte
’
s D ictionary,of Chemistry,
”.VOl.
VII., p. According to Tribe, silver deposited by copperalways contains copper
,i f the solution has absorbed ai r (Chem.
Vews, Vol. XXIV., .p Gold in contact with silver in a
cold or hot acid or neutral solution of a salt of silver receivesno deposit of silver (Raoult, Jour. Chem.Soc ,
Vol.XI., .p
Formation of Silver Peroxide. — F.Wohler states that ifa current from two Bunsen cells is passed through a dilutesolution of sodic sulphate or dilute sulphuric acid , bymeans of asi lver anode
,the latter becomes coated with argentic peroxide,
due to the action of ozone. With a solution of potassi c nitratesimilarly treated
,brown argentic oxide is formed with one
of potassic ferrocyanide the an ode becomes coated with whiteamorphous argentic ferrocyanide
, .and with one of potassicbichromate it becomes covered with reddish-black crystallisedargentic chromate (Chem.News, Vol. XVIII , p. Bresterstates that by electrolysing melted caustic soda, with an anodeof silver
,the anode dissolved and silver was deposited on the
platinum cathode, and that on cleansing ,the cathode with
n itric acid , a residue of black powder of platinumwas obtained(Chem. News, Vol. XVIII. p. I have on various occas ions noticed a similar residue after electrolysing melteda rgentic fluoride with platinum electrodes.
Electrolysis of Arg en tic Nitrate.. —Ag .N03. Molecular
weight 1 70. According to Brester,hydrogen
,evolved
either by electrolysis, by the decomposition of steam by redhot iron
,or by zinc or iron in dilute sulphuric acid
,reduces a
s olution of argentic nitrate, but not one of the sulphate ; also, ifa cathode of platinum
,whilst being used m the electrolysis of
d ilute sulphuric acid , be instantly d 1pped 1n to a solution of then itrate
,i t sometimes reduces the silver and sometimes not
(Chem.News, Vol , XVIII , p. Russel observed that purehydrogen reduces a solution of the nitrateto metal and nitrite
(Watts’
s“ D ictionary of Chemistry,
”Vol. VIII., Part II.,p.Sodium amalgam decomposes a strong solution of argentic
nitrate , and forms an amalgam of silver and mercury. Jouleformed the '
same amalgam,but richer in silver, by depositing
s ilver from the same solution into a cathode ~ of mercury.According to W. C. Reid
,thallium deposits silver from a solu
t ion of its nitrate by simple immersion (Chem. News, Vol. XII.,p . Metallic mercury
,in an acidified and moderately
s trong solution of the same salt,forms a “
silver tree ‘ or“ Arbor Dianee.”I observed that an aqueous solution ofargentic nitrate yielded its metal by simple immersion toarsenic
,antimony
,bismuth
,mercury, copper, brass, German
s ilver,n ickel
,iron
,lead
,tin
,cadmium ,
and zinc,but not to
s ilver,gold, or platinum. In an alcoholic solution of the salt,
antimony,bismuth
,zinc
,tin
,copper
,brass
,and the alloys oi
s ilver with zinc, tin, or lead, deposited silver by simple 1mmers ion , but 1ron did not.E lectro deposited nickel does not separate silver by simple
immersion from a solution of argentic nitrate (J.Spiller, Chem.
News, Vol. XXIV., p. Aluminium after six hours’ im
mersion begins to precipitate the silver,either from slightly
acid or neutral solutions, whether concentrated or dilute (A.
Cossa, Watts
’
s“D ictionary of Chemistry,
”2ud Supplement,
p. According to S.Kern , magnesium precipitates oxideo f silver from an aqueous solution of argentic nitrate (Chem.
News, Vol. XXXII. p.
Fused argentic nitrate,when electrolysed by a separate
c urrent, yields silver at the cathode and a large amount ofoxygen
‘
at the anode.
Formation of Arg entic Perox ide.— Ritter, in 18 14, disc overed that when a concentrated solution of argentic nitrateis electrolysed with two thick platinum wires as electrodes
( 72 )
peroxide of silver, Ag202, is deposi ted in crystals upon theanode
,and metallic silver upon the cathode. Fischer states
that these crystals always contain argentic nitrate (Watts’
s
“ D ictionary of Chemistry, Vol.V., p. I have also founda nitrogen compound in them.
To deposit coherent silver from a solution of the nitra t erequires the liquid to be weak and the current feeble. According to Luckow, the formation of peroxide of silver at the anodein a solution of argentic nitrate may be prevented by theaddition of glycerine, milk, sugar, or tartaric acid (Chem.News,Vol. XLII., p.Berthelot obtained sesquioxide of silver by the electrolysisof a 10per cent. solution of argentic nitrate. It was in theform of large, thick, black, lamillar, striated needles, of brilliant metallic lustre (Jour. Chem. Soc., Vol. XXXVIII., 18 80,p .
Electrolysis of Arg entic Fluoride. Ag .F. Molecularweig ht
= l27. I have observed that carbon and crystallineboron do not separate silver from fused argentic fluoride at ared heat
,but that crystals of si licon thrown upon the mel ted
salt become red hot, and burn vividly, producing silicicfluoride and separating silver ; also that hydrogen separatessilver from the semi-fluid salt. In an aqueous solution of thesalt, crystals of boron did not separate silver
,but crystals of
silicon deposited slowly crystals of silver. Stannous fluoridein contact with platinum also separated silver from such asolution. I observed also that in a mixture of solutions of
argentic fluoride,hydrofluoric and ni tric acids
,crystals of
s ilicon evolved spontaneously inflammable bubbles of silicid eo f hydrogen gas (Chem. News, Vol. XX., p. 28 , and XXIV.,
29 1pI fo)und the following to be the chemics-electric order of
various elementary substances in fused argentic fluoride,the
first being the most positive z— Si lver, platinum,charcoal of
lignum vitae, pallad ium, gold. And in a dilute aqueous solution of the salt, aluminium, magnesium,
silicon, i1id ium,
rhodium,and carbon of lignum vitae, platinum,
silver, pah
ladium,tellurium
,gold (Chem. News
,Vol. XXL
,p.
In a number of experiments of electrolysing argenticfluoride in a fused state in a covered platinum vessel wi thplatinum electrodes, with a current from six Smee cells
,con
d uction commenced before the salt had fused,and when the
salt had become quite liquid the conduction appeared to be asperfect as when the electrodes were united by a wire. Nosigns of genuine electrolysis were observable in ei ther case. Ialso electrolysed the fused salt by a current from ten Smeecells wi th an anode of highly ign ited charcoal of lignum vitae.Very little conduction took place ; the anode was , however,
t ( 7 4 )
; apparently of argentic peroxide, which econ stopped the cur
rent. To electrolyse it properly requires a feeble current, alarge cathode, and a very large anode (see Free. Birm. Phil.
Soc., Vol. IV.,Part 3
Electrolysis of Silver Perch lorate — A solution of argenticperchlorate
,containing free perchloric acid, with a silver
anode,is a remarkably good conductor. It conducted copiously
a current from a single Smee element, and was decomposedeven more readily than the chlorate. The
“
anode was rapidlycorroded
,and acquired first a thick loose coating of black
s olid matter, and then one of a dark green colour. To electrolyse this liquid properly requires a very feeble current, a.rather small anode, and a very large cathode (see Free. Birm.
Phil. Soc., Vol. IV.,Part
Electrolysis of Arg ento-sod ic Sulphite. — An aqueoussolution of this salt is said by Reseleur to possess a sing ularproperty. When a piece of metal is immersed in a solution ofanother one
,in which it coats i tself with that metal
,a portion
o f the immersed one dissolves, and produces an immense number of
°
minute electric currents which pass from an infin ity ofminute portions of the surface of the metal into the liquid
,
d ecomposing i t, and re-enter at other minute portions of themetallic surfaces, and deposi t an equivalent weight of theo ther metal as a coating upon the immersed one but in thisparticular solution a spontaneous chemical change also occursin the liquid itself
,the sulphurous anhydride of the argentic
sulphite takes oxygen to itself to form sulphuric anhydride,
and sets the silver free, and this silver adheres to any solidsurfaces present, t.e., to the immersed metal , and to the containing vessel. The sulphuric anhydride unites with some ofthe soda of the undecomposed portion of the sulphite , andliberates sulphurous anhydride
,and forms sulphate and bi
sulphite of sodium. This action is very similar to that whichtakes place in certain processes of coating looking-glasses withpure silver.A solution also composed of sulphite of silver dissolved
in an aqueous solution of potassic sulphite has been used ford epositing silver by the separate current process. It is a verygood one except that it gradually decomposes and deposits itssilver by the influence of light. A solution has also beenformed by dissolving argentic chloride in an aqueous solutiono f sodic hyposulphite. It easily yields its metal by electrolysis with a current, but under the influence of light it isd ecomposed , and its silver precipitated as argentic sulphite.
Electrolysis of Arg entic Molecularweight = 204. In an aqueous solution of the sulphate ofs ilver, antimony, tin , iron, copper, and the alloys of silver
w ith zinc, tin’
, or"
lead , depos ited the silver by Simple“
immer‘,sion
,but bismuth did not.
E lectrolysis ‘
of Arg ento-potassie Cyanid e.Molecular weight = 199 1. A solution of this salt
,containing
an,
excess of potassic cyanide,constitutes the ordinary silver
! plating liquid. It may be formed by dissolving the salt inwater, say one or two ounces
‘per’ gallon— the exact proportion is not material— and then adding about one-tenth of
‘
its weight of‘
potassic cyanide. Nearly the same mixture isobtained -by electrolysing a solution of potassic cyanide with asilver
'
anode,
'
un til silver is freely deposited ; in this case ,however
,caustic potash is formed in the liquid
,and gradually
becomes converted into carbonate by contact with the air.Electrolysis of the solution yields silver alone at the cathode
,
and at the anode argentic cyanide,which dissolves. A num
ber of modifications of,
this liquid have b een employed,such
as solutions formed by dissolving nitrate,chloride, or ferro
cyanide of si lver in one of potassic cyanide, but the aboVe
mixture is the best.By d issolving
'
some bisulphide of carbon in a strong solu
ltion of potassic cyanide, and adding a very minuteprop ortion ofthis solution occas ionally to the a bove mixture, the physicalcharacter of . the deposited silver is ‘greatly changed ; insteadof being soft and
'
somewhat dull w hite in appearance, i tbecomes hard and highly lustrous
,like burnished metal. I
have found by chem ical an alysis that .it contains a minute
preportion of sulphur.By electrolysing a 33 per cent. aqueous solution of methy
lamine with a silver anode and a feeble'
curren t from a singleSmee cell, the -anode slowly dissolved, and a loose deposit ofsilver crystals formed upon the cathode. Somewhat sim ilarresults were obtained with a strong solution of trimethylamine.Blagden s tates that the desilvering of lead is facilitated by
dissolving about half a per cent. of zinc in ' the refined metalat 540°C.,
and passing a voltaic current through it by meansof copper wires
,un til all
,
the .zinc h as risen to the surface !‘This crust contains the silver, and may be removed after themelted mass
'
.has'
fallen to The process must berepeated several times.For a solution fit for silvering iron ,
‘
seeWatts’
s“ D ictionary
of Chemistry,
”Vol. VIII., Part II., p. For depositionof silver from a pasty mixture of salts by simple contact, seeRoseleur, Jour. Chem. Soc., Vol. XXXIV.
,1 878 , p. 538. For
the electrolytic analysis of silver, see Chem. News, Vol. XLII.,p. 331 and p. 7 6 Watta’s “ Dictionary of Chemistry,
”Vol.
VII.,p. 7 90 Jour. Chem. Soc., Vol. XXXVIII 1880, p. 747.
Separation of Mercury.— Hg. Atomico
weight= 200 A-
, dyad cation. ~ Iahave observed that solutions '
of fgmercurous
( 7G )
salts have their metal deposited by simple immersion, by
arsenic,antimony, bismuth, zinc, cadmium, tin , lead , iron,
copper,brass
,and the alloys of silver with zinc
,tin
,lead , or
copper. Iron deposited mercury from a solution of mercuryacetate. A. Cossa states that aluminium deposits mercury bysimple immersion in aqueous solutions of mercuric nitrate
,
chloride,and cyanide ; also from a solution of mercuric
chloride in alcohol , and of mercuric iodide in one of potassiciodide (Watts
’
s“ Dictionary of Chemistry,
”Vol.VII., p.Thallium deposi ts mercury from an aqueous solution ofmercurous sulphate (W. C. Reid
,Chem. News
,Vol. XII
p. Solutions of salts of mercury have been electrolysedby the mutual contact of two metals in them (seeGladstoneand Tribe ’s experiments, Phil. May ,
4th series,Vol. XLIX.,
p. 245)-1 have observed that by passing a current from a mercuryanode through dilute sulphuric acid into a platinum cathodethe latter soon ac uires a coating of mercury. E. Obach
states that a liqui alloy of sodium and mercury showed nosigns of electrolysis by passing through it an electric current.
Electrolysis of Nitrate of Mercury — Copper immersedin a solution of nitrate of mercury deposi ts the latter
,and
forms an amalgam. By electrolysing a solution of cupri csulphate into a cathode of mercury a similar alloy is formed.An aqueous solution of mercuric nitrate has been used byelectro-platers for “ quicking”the surfaces of articles previous to plating them. A solution of nitrate of mercuryyields its metal to bismuth
,zinc , cadmium,
lead, iron, orcopper
,but not to silver, gold , or platinum,
by simple immers1on.
Electrolysis of Mereuric Ch loride.— Hg .Cl2. Moleular
weight = 27 l . From an aqueous solution of this salt magnesium deposits mercuric oxide and calomel (Commaille, Chem.
News, Vol. XIV., p.A solution of mercuric chlmide, slightly acidulated with
sulphuric acid , in a platinum vessel cathode, was electrolysed ,and the amount of mercury in it determined by means of acurrent from six Bunsen cells
,the anode being a sheet of
platinum. Mercurous chloride was first deposi ted,but at the
end of one hour all the salt was reduced to mercury so perfectly that the supern atant liquid was not rendered cloudy byaddition of ammonia. By running a stream of water finallythrough the vessel whilst the current was passing the wholeof the mercury was obtained in a pure state (F.W. Clarke,Report of theChemicalSociety of Berlin , No. 12, Gladstoneand Tribe noticed that when a weak current was passedthrough ta solution of mercuric chloride into a cathode of
( 7 7 )
platinum a film of mercurous chloride was deposited,but if
the current was stron g, metallic mercury was set free.
Electrolysis of Potassio Mercuric Cyanid e.— 2KCy.Hg .Cy2. Molecular weight= 382°2. The solution of this saltreadily deposits its metal by simple immersion upon copper
,
and various of the base and alkali metals,and is therefore
used by electro-depositors to prepare , by the process termedquicking
,
”the surfaces of metal articles to receive an adherentd eposit of silver. It also readily yields its metal by means ofthe other methods of electrolysis.
Electrolytic Movements of Mercury.— Ia consequence ofbeing a liquid , mercury exhibits certain peculiar phenomena ofmotion and alteration of form when used as an elec trode.This effect appears to be partly a consequence of a film ofoxide or other salt formed upon it when it is an anode
,and of
hydrogen or other substance formed upon it when a cathode,
and partly also of simple electrification. H. Herwig hasobserved that a drop of mercury placed on a glass plate
,and
s trongly electrified by either pole of a Holtz machine,becomes
flattened,and if the mercury is in a narrow glass tube its capil
lary depression is greatly diminished. The effect is greatestwith the positive pole
,probably in consequence of the higher
tension of that pole (Page.Ann. CLIX , pp. 489 Asearly as the year 1801 , Gerboin noticed some of the electrolyticmovements of the metal
,and the phenomena have since been
investigated by Sir H.Davy,Sir J.Herschel, Serullas, Erman,
Runge,Pog gend orfl
'
,Gmelin, and others (seeGmelin
’
s Handbook of Chemistry,
”Vol. I., pp. 38 1 Also by T.
S. Wright (Phil.Mag ,Vol. XIX.
,1 860, pp. 129 by R.
Sabine (Phil. Mag . Vol. II., p. and Th. du Moncel
(Watts’
s“D ictionary of Chemistry, Vol.VIII ., Part I., p.
The movements have also been applied by Lippmann to themeasurement of extremely feeble electric polarities in h is
c apillary electroscope and also to the production of motionin h is capillary electric engine. In most of these cases theelectrolyte employed was dilute sulphuric acid.
Electrolytic Sounds.— By employing as an electrolyte as olution of potassio mercuric cyanide, wi th electrodes of theliquid metal
,I discovered that the mercury emitted electrolytic
s ounds, and became covered on its surface with minute waves,s ymmetrically disposed
,and beautiful in appearance. These
waves and sounds appear to be due to the rapid alternate' for
mation and destruction of films upon the mercury by .electrolytic action. The best solution for producing it consists of 10grains of mercuric cyanide and 100 of pure potassic hydrated issolved in 251L ounces of aqueous hydrocyanic
‘ acid ofScheele’s strength,
”and the liquid filtered. The waves and
sound occur at the cathode. T hemercury may be contained'
in two smallwatch glasses submerged in the solution contained .
in a large,flat-bottomed glass basin. The current employed
may be from two Gro‘
ve or five Smee elements,and con
veyed into the electrodes by platinum wires protected fromthe electrolyte by means of glass tubes. By suitable tests Ifound that during the emission of the s ounds the electri ccurrent was rendered to a considerable extent intermittent
,
and that the arrangement might be employed for similar usesto those of a voltaic break-hammer ; the intermittence, however
,is much less perfect (see Proc.Roy. Soc., 18 61 and 1862)
‘
For the detection and estimation of mercury by electrolysis,
ste F.W. Clarke, Jour. Chem.Soc.,Vol.XXXIV.
,187 8 p. 9 16 ;
also Vol.XXXVI., 18 79 , p. 9 76 ; J.Lefort, ibid .,Vol.XXXVIII.,1880, p. 5 10 Watts
’
s D ictionary of Chemistry,Vol.VIII.,
Part II., p. J. B. Hann ay estimates mercury electrolytically by pas sing a current through a solution of its sulphateinto a platinum dish containing it.
Separation of Copper.— Cu. Atomicweight = 63 '
5 . Adyad .
cation. By simple immersion of magnesium in a solution ofcupric chloride
,Brunswick green, but no metallic copper,
appears ; but in one of cupric sulphate,the metal
,together
with its hydrated protoxide, and a green subsalt are produced
(Commaille,Chem. News, Vol. XIV., .p From a solution .
of cupric nitrate or sulphate,aluminium after two days’
immersion deposits copper ; in the nitrate solution a greenbasic salt of copper is also produced ; but if a minute amountof alkali chloride is added to either of these liquids, deposition commences at once. From a solution of cupric chlorideor acetate, aluminium separates
,
copper at once,but the
deposition afterwards p roceeds slowly (A. Cossa, Watts’
s .
“ Dictionary of Chemistry,”Vol. VII , p. According to
Smee iron does not decompose a neutral solution of cupricacetate, nor alkaline ones of ammonuret, ammonic nitrate, orammonic sulphate of copper
,but decomposes one of .the nitrate.
Z inc amalgam deposits copper from neutral solutions of cupricsalts
,and forms a copper amalgam (Damour, Jour. Pi ac.
Chem ,Vol. XVII., .p By adding crystals of silicon to
melted protoxide of copper, I observed that sudden incandescen ce and a full white heat were produced , and metalliccopper was separated. Thallium deposi ts copper from the
solution of cupric nitrate,sulphate, and acetate (W. C. Reid,
Chem. News, Vol. XII., .p Raoult states that gold incontact with copper, in either a cold or boiling acid or neutralsolution of a cupric salt
,receives no depos it of copper (f our.
C hem. Soc , Vol. XI. p.Smee states that the use of solutions of the hyposulphite,
ammoniuret, or acetate of copper, with a separate current,
( 7 9 )
offers no advantages for depositing copper,because they are
difficult to decompose,and require a current from several cells,
that a copper anode is but little corroded in a solution ofsulphocyanide of potassium
,and the solution does not hold ‘
much dissolved metal ; also that the anode is very slig htlyacted upon in a solution of tartrate of potassium. M. P.
Schutz enberger found from five to ten per cent. of cuprous,
oxide in copper electro-deposited from an acetate solution (J.
B. Mackintosh Chem. News, Vol. XLIV.,p. 27 9, and Vol.
XLV.,p.
Formation of Nitride of Copper.— By passing a currentfrom six Grove cells into one end of a solution of sal am
moniac contained in a’
long glass trough by means of a copperanode, and out of the liquid at the distant end by a platinumsheet cathode
,the liquid b ecomes blue
,and a heavy solid
nitride of copper of a chocolate colour collects at the cathode(Grove, Phil. .Mag ., 3rd Series, Vol. XIX.,
p.’
Electrolysis of Cupric Nitrate .— Cu.2No3. Molecular
weight = 187 '5. I observed that a solution of cupric nitrateyielded its metal te
'
zino, tin , lead , or iron, by simple immer
sion , but not to nickel, copper, silver,gold
,platinum
,or an ti
mony. J. B.Mackintosh states that in the electro-depositionof copper from a nitrate or ?sulphate solution containing citricor tartari c acid
,the deposited metal is not pure. With the
nitrate solution containing citric acid,electrolysis was attended
by a strong odour of hydrocyanic acid (Chem. News, Vol.
XLIV., p. 27 9 , and Vol. XLV., p.
Electrolysis of Cupric Fluoride.— Cu.F2. Molecular weight
1015 I observed that copper was separated from its
melted fluoride by adding fragments of magnesium also thatcrystals of silicon immersed in a solution of the fluoride evolved
gas, and became instantly coated with copper.By means of a separate current from six Smee cells, a
,
platinum wire helix anode and a copper wire helix cathode , Ielectrolysed fluoride of copper
,fused at a bright red heat in a
deep copper cup. Conduction was copious, as if the salt wasa metal
,and an acid vapour was evolved. The anode was un
altered,no copper was deposited , but the cathode had lost
33 5 grains in weight by corrosion near the surface of’
themelted salt ; t he copper vessel was also similarly acted uponin several experiments and caused to leak. The phenomenawere much like those obtained with melted argentic fluoride.A solution of cupric fluoride in pure dilute hydrofluoric acid ,
with copper electrodes, conducted freely the current from asingle Smce element, and yielded a good deposit of copper.
‘ Electrolysis of Cupric‘
Ch lorid e. MolecularAluminium acts briskly on a solution of
cupric ch loride at 16°
C,setting free copper, hydrogen, and
aluminium oxychloride. the composition of wh ich varies witht he temperature (D. Tommasi , Jour. Chem. Soc., Vol. XLII.,1 882, p. Vol. XLIV.,
1883, p. 19 ; Chem. News, Vol.
XLVI., p. Copper is at once deposited from its chloride,
and more slowly from its acetate, by aluminium (A. Cossa,
Watta’s “ D ictionary of Chemistry,”Vol.VII., pp. 54 and
I observed that in a solution of cupric chloride, bismuth, zinc,tin
,lead
,and iron deposited copper by simple immersion
,
but nickel, copper, silver, gold, platinum,or antimony did not ;
also that in a solution of sub~chloride of copper in strongaqueous ammonia zinc received a deposit of copper by simpleimmersion, but tin , lead, iron, nickel, copper, silver
,gold
,
platinum,bismuth
,or antimony did not. When a copper
platinum couple is immersed in a dilute solution of this saltinsoluble white cupreous chloride is deposi ted on both themetals. With couples formed of zinc-platinum or magnesiumplatinum the action is stronger, and metallic copper is d epositedup on the platinum (Gladstone and Tribe , Phil. Mag ., 4th
Series, Vol. XLIX., p.
M.Weis Kepp coats iron with copper by simply immersingit in a bath compo sed of 10 parts of cupric chloride
,10of
nitric acid , and 80 of hydrochloric acid of specific gravity
(Chem. News, Vol. XXL , p. According to O.
Gaudain ,articles of cast iron, wrought iron, or steel may be
c oated with copper by dipping them into a melted mixture offluoride and chloride of copper, with five or six parts of cryolite
,
and a little basic chloride, in a plumbago crucible (Jour. Chem.
Soc., Vol . XI., p. In some cases, copper 1s extractedfrom sandstone , which contains i t in small preportion , by d iss olving the ore out by dilute hydrochloric acid, and immersingpieces of scrap iron in the liquid until they are wholly d iss olved, and metallic copper is left.t en 9. feeble electric current is passed by means of copper
electrodes through a solution of chloride of copper in dilutehydrochloric acid , the anode becomes covered with snow-whitec rystals of cupreous chloride, and the cathode with a thick deposit oi loose copper (Chem.News
,Vol.XXII ,
p. If a solut ion of cupric chloride was electrolysed by a feeble current withplatinum electrodes, chlorine appeared at the anode andc upreous chloride at the cathode but if the current was strong,m etallic copper was also deposited upon the edges of the catho de
(Gladstone and Tribe). Smee states that a solution of this salt.is less readily decomposed by an electric current than one of then i trate
,but more readily than one of the sulphate
,that it is
a lso one of the worst liquids for the electrolytic separation ofm etallic copper, and that the deposited metal is apt to assumea very peculiar appearance. He also states that a solution ofthe ammonio-chloride is a bad one
,having a tendency to
( 8 9 )
iir'
nfié'
rsing'
clean”! articles '
oi ironwor'
.s teel in contaét with apiece of zinc or lead 1n this liquid a sufficiently long period o ftime they receive a strongly adherent co ating of copper, of anydesired thickness. Pure tin in contact with zinc in thisliquid does not become coppered , but oxidises, and its oxidegradually precipitates as red suboxide all the copper of thesolution.Copper is also deposi ted by means of the contact of two
different metals in two different liquids (the single cell process for the purpose of coatie cast-iron cylinders for calicoprinting (see Chem.News, Vol.X X., .p 219 ; also Jour. Chem.
Soc., Vol. XIII., .pA good solution for depos iting by means of a separatecurrent is composed of t four p arts t of crystallised cupric sul
phate (Cu.SO, ,5H
20) and one o f sulphuric acid, in 1 8 or 20
of water. Sometimes sulphate of zinc or of potassium is addedto such a solution 1n order to improve the depos it.According to A. Long, copper electro-deposited by a
s eparate current from a solutio n of its sulphate containsminute amounts of hydrog en, carbonic oxide, carbonic aubydride
,ahd water (Watts
’
s“ Dictionary of
Elimination of Impurities from'
Copper by means o fElectrolysis — Very few metals are likely to .be e eleetro
deposited along with copper - from the usual acid sulphatedepositing solution by -a separate current ; the most likely oneis cadmium. In the elec trolysis of that solution with an
anode of ordinary copper,a considerable amount of black
insoluble mat ter separates at the anode. An .analysis ofthis substance by JMax Duke of Leuchtenberg g avezthe following
Oxygen 24 8 2
Copper.AntimonyArsen ic " 7 ‘20Silver 2
Sulphur
Nickel 2‘26
Silicia .
1'27‘
98
8 6Van adium ‘64
‘
44‘30‘15 99 6 9
(Erdmann, Jour. Vol. XLV., pp. 460
The following are comparatively recent analyses kindly supplied to me by a friend. They are those of the powder from
“c opper plates .used as anodes in depositing copper on statues,850:
C opper 85'
f500
WVater an d oxy
gen
ArsenicSilverSulphuric acid .
Insolubleeai thvmatter
An timony1Iron
Bismuth
AluminaCh lorin e
f‘
iocco
“ Refining of Crude Copp er by E lectrolysis — This proJeese is carried ' out on a large scale by Messrs : Elking tonpat
their copper Pembrey, South wWales.‘ .The ! proc esss imply consists in making large slabs of the crude metal
,
obtained aby'
the ordinary smelting process, .anodes : in thezusual
cupric sulphate~
solution,
-and passing. currents from numerousdynamo electric machines through t the solutions; u ntil zu‘thes labs are wholly dissolved and their copper t depositeda
'.Ea
’
chc urrent -passes in
'
an : undivided state through -a series tof asuch
electrodes and’
solutions in order te diminish the cost of ithe
process .
The impurities which separate vary, of .course,~ with .the
fid ifl‘
erent samples of crude metal. In : the : process; . toxygen ,sulphur
,selenium
,carbon
,boron
,silicon
,-and arsenic a re onot
d eposited at the cathode. Silver is. precipitated : at thet anodeby the traces of hydrochloric acid present in the common
( sulphuric acid employed. Gold falls as metal at the anode,lead as sulphate ; carbon and metallic sulphides
,also selenium
and silica,fall at the anode. Z inc
,iron
,tin; cadmium,
cobalt,n ickel
,and antimony are more or less dissolved , butpbeing
les'
s readily deposited than copper, remain in solution. Arsenicfalls as an arsenide, and t hemetal most
.likely. to be deposited ,viz., cadmium,
is present so rarely, or in so small an amount,as to remam i n solution.
Electric ' — Copper being a very suitable metalfor the purposes of engravers and printers
,the electric corro
sion of anodes in a solution eof cupric sulphate was soon appliedto engraving and etching. Copper rbeing also a metal easilyd eposited, the process of electro-deposition of ~
00pper in solutions of . its sulphate was also applied ; to .the m ultiplication of
0 2
Lead
NVater and oxy
g en
Copper
An timon‘
Sulphur
Silver
Arsen icEarthy matter
Bismuth
Chlorine
Iron
NickelOrg anic matter
.Gold
Loss
CopperSulphurIron
In soluble earthymatter
Organ ic mat ter
Lead 205S ilver "55
Loss‘
20
( 84 )
engraved plates, the copying of set up type, the manufactureof works of art
,and even of colossal statues, &c. The details
of these and other technical uses of electro-chemical actionsmay be found described in works on Electro-Metallurgy.For the uses of electrolysis in the metallurgy of copper by
the processes of Becquerel, Keith , and Patera, see Jour. Chem.
Soc., Vol. XXXVI , 18 79, p. 7 60 also Blas and Miest,Chem
News,V ol. XLVI p. 121. The latter also apply electrolysisto all kinds of ores.
Electrolysis of Cuprose Potassic Cyanide.— There are
several cuproso cyanides of potassium. The one usuallyemployed for electro-deposition is formed by dissolving greencuproso cupric cyanide to the point of saturation in a solutionof potassic cyanide, and then adding some more of the potassicsolution ,
and using the mixture at a temperature of about1 50
°
F. The base metals much less readily deposit copperby simple immersion in this liquid than in the ordinary cupri csulphate solution. By the passage of a separate current thissalt is also less readily decomposed than cupric sulphate, andhydrogen is freely set free at the cathode along with theCopper.
.Various mixtures of salts containing potassic cyanide havebeen employed for depositing copper upon base metals.Roseleur recommends the following — Rub 20parts of crystal~
lised verdigris to powder in a little water, add to it with stirring 20parts of washing soda dissolved in 200parts of water,mix the solution with one of 20parts of bi-sulphite of sodiumd issolved in 200 parts of water, and add the mixture withstirring to a solution of 20 parts of pure potassic cyanide dissolved in 600parts of water ; then if the mixture is not colourless, add more potassic cyanide until it is so. It may be usedeither hot or cold. A second one he recommends is composedof 20parts of strong aqueous ammonia, 30of sodic bi-sulphite,35 of cupric acetate, 50of potassic cyanide of 70perand of water. The ammonia and copper salt are dissolved in one portion of the water, and the cyanide and bisulphite in the other, and the two solutions mixed. If theresulting solution is at all blue, more potassic cyanide must beadded to render it colourless. This mixture also may be usedhot or cold.Another liquid employed for the same purpose may bemadeby dissolving 40parts of the blue ammoniuret of copper and80parts of potassic cyanide in about parts of water.W. H. lValenn recommends cyanide of copper dissolved tosaturation in an aqueous solution of equal parts of potassiccyanide and ammonium tartrate, and sufficient oxide and
ammoniuret of copper added to prevent evolution of hydrogen.at the cathode when the liquid is used at 80
°
C. with a current
( 8 5 )
from a single Smee element. Dr. Elsner used,a solution
composed of one part ( f potassic bitartrate boiled in ten partso f water, and as much freshly-prepared and wet hyd ratedc upric carbonate which has been washed wi th cold water
,
s tirred wi th it, as the liquid will dissolve. A small quantityo f potas sic carbonate is th en added . He states that a copperanode d issolves readily in this mixture.According to F.Weil, by employing an alkaline solution in
which cyanides are replaced by organic acids or glycerol ,copper m ay be firmly deposited by a separate current onwrought iron , cast iron , and steel
,and the acids or glycerol
are n ot decomposed (Jour. Chem. Soc., Vol. XLII., 1882,
. 670)pCopper has been deposited upon iron by the combinedaction of s imple immersion and of .a separate curren t in asolution of one part of cupric oxalate and a large exces s of
potassic bi or quad-oxalate , in ten to fi f teen par ts nf water
(Watts’
s“ D ictionary of Chemistry
,
”Vol. VIII., Part II.,p.
'
The physical properties of‘
the copper depo sited from thev arious mixtures, and from each solution at different temperatures
,or by different strengths of current
,vary considerably.
A trace of carbonic bisulphide in the cupric sulphate solutionm akes the deposit brittle, the anode also becomes black
,but if
there is also a great excess of acid, i t sometimes becomes verybright and if the liquid also contains much potassic sulphate,the deposited copper is said t o be bright. The deposit alsof rom the cyanide is usually bright when the current is strong
,
and of a dull aspect when it is we ak. According to Favre,
electro-deposi ted copper contains more h eat than the rolledm etal (Watts
’
s“ D ictionary of Chemistry ,
”Vol. VII., p.For the absorption of gases by deposited copper
, see Watts’
s
“D ictionary of Chemistry,”Vol.VII., p. 383.
Analysis of Copp er Ores by Means of Electrolysis.— As
this series of articles is not of a technical character very fewremarks are admissible on this subject. To carry out als > proc esses of electrolytic analysis successfully
,requires a knowledge
o f analytical chemistry, because the methods in nearly all
c ases (with other metals as well as with copper) are combinat ions of ordinary chemical and electro-chemical ac tions.By electrolysis all the copper is separated from solutions
c ontaining free hydrochloric acid on the addition of ammoniumo r sodium chlorides, or sodium acetate ; similarly from solutions containing excess of ammonia
,ammonium carbonate
,or
potas s i c cyanide. From a solution containing mercury, S
’lVeI‘,bismuth , and copper, the last two metals are only d epositedafter the greater portion o f the first two has separated (C.Luckow
,Jour. Chem. Soc., Vol.XXXVIII., 1880, p.
( 8 6 >
The electrolytic determin ation of the amount of copper present in a liquid is more readily made than that of almost anyother metal
,and this agrees with the usually extreme degree
of purity of the deposited substance. The last traces ofcopper may a lso be perfectly precip itated in a coherent statefrom a solution of blue vitriol containing two platinum elec~trodes, by a current of suitable strength. The deposited .
copper, however, is not perfectly pure if tartaric or
citric acid is present. The electrolyti c process is
sively used. Details of it may be found in Watts’
s“ Dic u
tionary of Chemistry,”Vol. VII., pp. 384, 7 90; Vol. VII I
p. 5 59 : Chem.News, Vol. XIX., 18 69 , p. 221 XXIV.,pp. 100 '
and 172 ; XLI., pp. 25 , 213 ; XLII., p. 331 ; XLIV., 188 1 ,p. 27 9 ; XLV.
,1882, p. 101, and XLVI ,
p. 105 : Jour. Chem.
Soc., 18 7 6, Part II., p. 1 15 ; 1 87 7 , Part I., p.340; Vol .XXXVI.,
1 87 9 , p. 27 6 ; Vol. XXXVIII., 1880, pp. 282 and 583 ; Vol.XL ,
188 1 , p. Vol. XLII., 1882, pp. 428, 660,and r
Separation of NickeI.— Xi. Atomic weight = 59. A dyadcation. Less read ily deposi ted than copper. . From slightly ‘
acid solution of salts of protoxide of nickel , magn esium de
posits by simple immersion metallic nickel and hydrogen
(Roussin, Chem. News,Vol. XIV.,
p. 27 Z inc amalgamdeposits nickel from neutral solutions of nickel salts by simpleimmersion
,and forms an amalgam (Damour, Jour.Prue.Chem ,
XVII,p.
By contact with a second metal, nickel is also in some casesdeposi ted from its solutions . Stolba takes a boiling hot, onethird saturated solution of chloride of zinc
,in a copper vessel ,
renders i t clear by adding just suffi cient hydrochloric acid,then adds a few particles of zinc
,sufficient to cause a slight
deposit of zinc upon the copper. He next adds either chlorideor sulphate of nickel , until the mixture is distinc tly green.The metals to be coated
,via ,
cast i ron,wroug ht iron,
steel,brass
,or copper, are then immersed in the boiling solu
tion in contact with zinc until they are coated (Watta’
s Dictionary of Chemistry,
”Vol. VII., p. 850 also Chem. News,
Vol. XXXV.,p. C.Méne coats either iron , steel , zinc,
lead , copper, or brass with nickel , by immersing it in a boiling hot neutral solution of chloride of zinc, containing fragments of nickel. If the liquid is acid, the deposi t appearsdull (Chem. News, Vol. XXV., p. A nickel-gold coupleproduces no deposi t of n ickel in acid or neutral, hot or cold , solutions of salts of nickel (Raoult, Jour.Chem.Soc.,Vol.XL , p.An aqueous solution of cream of tartar and hydrated nickeloxide
,with a little soda
,gave by the separate current process
peroxide of nickel at the anode D ictionary'
of Chemistry,”Vol. VII., p.
( 87 )
s -Electrolysis of Nitrate of Nickel.— Ni.2NO3.
' Molecularweight = 183. Nickel may be deposited by a separate currentfrom a solution formed by dissolving one part of nitrate of
,
nickel in one part of strong aqueous ammonia, and then adding20to 30times its volume of aqueous bisulphate of sodium ofspecific gravity (Roseleur). I have always found thatwhen n ickel solutions contained nitrates the deposited metalwas of a -bad colour.In France a solution is prepared by dissolving four parts of
nickel n itrate in four,parts . of aqueous ammonia and 150parts
of water holding in solution 50parts of acid sodium sulphite.A very feeble current is used
§Boden
, Watts’
s“ D ictionary
of Chemistry,
”Vol. VIII., Par t I., p.Electrolysis of Fluoride of Nick el. — By immersmg crystals of wsilicon in an aqueous solution of nickel fluoride, containing free hydrofluoric acid, I observed that they did n ot
‘
become' coated with -metal ; but by heating the crystals withten times their weight of nickel fluoride to redness in a porcelain crucible, vivid incandescence occurred, and nickel was .deposited and melted by the great heat evolved.
Electrolysis of Ch loride of Nick el. — Ni.010. Molecularweight = 130. The simple immersion of Copper in a solution
b
of the double chloride of n ickel and sodium is suffi
cient to deposit the nickel (Becquerel, The Chemist, Vol. .V.,
p. Z inc throws down the metal from a solution of.nickel chloride previously T endered a lkaline b y addition ofammonla.
One of the first really good liquids for depositing nickel bymeans of a separate current for practical purpo ses appears to havehad its origin in the following experiments published by me z
“‘I have depo sited nickel in the state of reguline white metalfrom a solution of the deuble chloride of nickel and ammonium
,by making a lump of metallic nickel the anode in a
strong aqueous solution of hydrochlorate of ammonium (salammoniac), and passing a strong current until the liquidacquired a pale grach ish blue colour (Pharm. Joan , Vol. XV.
NO. 9 , September 1 , 1855 , pp. 106 and T. Fearn, mi18 72, published the composition of a solution for depositingnickel
,viz.
,24 parts of sal ammoniac dissolved in 160parts of
water, and the liquid then saturated with protoxide of nickelat 120°
F.
’
Martin and Dalmette dissolve grammes of citric acid,500
’
of sal ammoniac (or ammonium sulphate) and 500“of
nitrate of ammonium in 15 litres of water ; heat the liquid to80
°
C ,and saturate it with recently precipitated hydrate of
nickel,then add 2h l itres of aqueous ammonia ; dilute to 25
l itres, and after cooling add 500 grammes of ammonic car
( 88 )
bonate, subside the mixture, and fi lter the l iquid. Use thesolution at 50
°
C. (Watta’
s“ D ictionary of Chemistry
,
”Vol.VIII.
,Part II., p.
Electrolysis of’
Sulph ate of Nickel. — Ni.SO4. Molecular
weight = 1 5 5 . Magnesium deposits nickel by simple immersion from a solution of nickel sulphate (Commaille, Chem.News,Vol. XIV.,
p. Z inc throws down the metal perfectlyfrom a solution of nickel sulphate rendered alkaline by addi~tion of ammonia (A. Merry, Jeur. Chem Soc., Vol. XIII ,
311pThe)best solution for electro-depositing nickel ismadeeither
by dissolving the crystallised double sulphate of nickel andammonium,
in the proportion of half a pound to a pound,in a
gaIIOn‘
of water, or the double chloride of nickel and ammonium may be used instead. A large anod e of nickel shouldbe employed. Bottg er states that the best solution for depositing nickel by means of a separate current is made byadding to crystals of prota sulphate of nickel as much liquidammonia as is necessary to dissolve them (Pharm. Jour., Vol.III., 1843, p. Nagel dissolves two parts by weight ofcrystals of sulphate of nickel in a mixture of six parts ofaqueous ammonia of specific gravi ty 9 09 and thirty parts ofwater, and uses the mixture at a temperature of about 100
°
F.
Another liquid is composed of 100parts of sulphate of nickel ,5 3 of tartaric acid, and 14 of hydrate of potassium,
dissolvedin a suitable proportion of water. It is said t ) yield a brightdeposit of metal. Some recipes include nitrate of ammonium,
or nitric acid , which is objectionable (see also A. C. and E.
Becquerel,Comptes Rendus, Vol. LV., p. 18 also Kayser
,
Jour. Chem. Soc., Vol. XXXIV.,1 8 78 , p.
Another nickel solution is composed of 8 7 5 parts of nickelsulphate, 20of ammonium sulphate, 1 7 5 of citric acid, and 2l itres of water (Hesse, Watts
’
s“ D ictionary of Chemistry,
Vol. VIII., Part II., pp. andMore recently n ickels ulphate
-depositing solutions containing borax have been employed. I analysed one
,and found it
to contain sulphate and chloride of nickel,borax
,and a small
quantity of ammonia. AMr.Powell,of Cincinnati
,adds lgoz . to
l o z . of benzoic or pyrogallic acid to each gallon of the ordinarynickel plating
‘
solution to improve it.”A solution of ferrocyanide of nickel dissolved in aqueouspotassic cyanide has also been employed for depositing themetal.In the deposition of nickel from the solution of the double
sulphate of nickel and ammonium with a cast nickel anodethe anode disintegrates to a loose powder upon its surface, andalso by solution of the nickel a loose coating of impurity accumulates upon it, and fal ls to the bo ttom of the liquid and col
( 90 >
solution of chloride of zinc containing fragments of cobalt
(Chem.News,Vol. XXV., p.
Formation of Peroxide of Cobalt — An aqueous solutionof cream of tartar and hydrated cobalt oxide, with a littl esoda dissolved in it
,yields
,with a separate curren t
,a peroxide
of cobalt,exhibiting magnificent colours upon the anode (W.
Wern icke,Watta’s “ D ictionary of Chemistry,
”Vol. VII.,899)I)By passing a separate current through a solution of oxide ofcobalt in aqueous potassic cyanide
,hydrogen and a small
quantity of cobalt are deposited.According to Troost and Hautefeuille
,laminae of electro
deposi ted cobalt sometimes contain as much as thirty-fivetimes their volume of hydrogen (Chm . News, Vol. XXXI.,pl l 96)
Electrolysis of Fluoride of Cobalt Molecularweight = 97 . I electrolysed a solution of this salt in puredilute hydrofluoric acid , by means of a current from a singleSmee cell
,with an anode of cobalt and a cathod e of copper,
but only a film of black powder appeared on the cathode intwelve hours.
.Electrolysis of Ch loride of Cobalt — " C005. Molecular .
weight = 130. Magnesium decomposes a solution of cobalt .
chloride,with evolution of hydrogen and separation of a green
salt contain ing cobalt oxide (8 . Kern,Jour. Chem. Soc., 18 7 6,
Part I.,p. Copper immersed in a solution of the double
chloride of cobalt and sodium acquires a coating of cobalt
(Becquerel , The Chemist, Vol. V.,-
p.
In a solution composed of 20 parts of sal ammoniac,40 of
chloride of cobalt,20of aqueous ammonia, and 100of water,
a'
bri llian t deposit of metallic cobalt was produced Upon a
cathode of brass or copper, .by means of a current from two
Bunsen cells (M. R.Boettger, Chem.News, Vol.XXXV.
,p. 166
,
also Jour. Chem. Soc., 187 7 Part II., p. 375 . To deposit themetal , dissolve five ounces of its dry chloride in a gallon ofdistilled water, and make the solution slightly alkaline bymeans of aqueous ammonia. Pass a current from three tofiveSmee cells through .the solution by means of an anode ofcobalt (Telegraphic Journal, Vol. II., p. By means of a.separate current, an anode of cobalt, and a concentrated solution of the chloride
,with its excess of acid neutralised by
caustic ammonia, Becquerel obtained deposi ts of the metal,brilliant
,white, hard , and brittle, and possessing magnetic
polarity. He~ observed that part of the chloride of the solution was set free during the electrolysis
, and that if the liquidcontained iron the greater portion of it was not deposi ted with .
the cobalt (Chem. News, Vol. VI., p.
( 91 )
iElectrolysis of , Sulphate of Cobalt Molecular
weight 15 5 . Magnesium slowly deposits hydrated oxide ofcobalt from a solution of the sulphate (Commaille, Chem. News
,
Vol. XIV.,p.
‘By means of a separate current, cobalt is completely precipitated in the metallic state from an aqueous solution of doublesulphate ‘of cobalt and ammonium , if free ammonia is present
(H.Fresenius and F.Bergmann , Chem.News,Vol. XLII., p. 7
Caiffa deposited hard tenacious cobalt of good colour from an r
aqueous solution of the double sulphate of cobalt and am
mon ium'
by means of a separate current (Chem. News, Vol.XL., p :
Electrolytic Analysis of Compounds of Cobalt.— See
Chem. News,Vol. XLI., p. 25 p. 75 Vol. XLVI ,
p. 105 Jour. Chem. Soc., 18 7 7 , Part I.. p. 341 1 8 7 7 , Part II.,p. 925 Vol. XXXVI. 187 9 , p. 5 88 ; Vol.XXXVIII., pp. 28 4,5 83
,and 7 7 1 ; Vol. XL., 188 1 , Vol. XLII.,
pp. 8 96,
Separation of Iron . Fe. Ele’
ctro-chemical‘
equivalent"
28. A dyad cation. From slightly acidified solutions of
ferrous and ferric salts,magnesium deposits iron and hydrogen
g as (Roussin , Chem.News,Vol. XIV., p. 27 Iron in contact
with gold , in acid or neutral, cold or hot solutions of salts ofiron
,produces no metallic deposi t (Raoult, Jour. Chem.
Vol. XI., p. Metallic iron reduces ferric to ferrous saltsat ordinary temperatures, Whilst platinum has no such effect.Nevertheless, if these two metals are connected together, theyreducethe ferric salt m ore rapidly than iron alone does, and
the reduced salt forms upon the platinum also, as may be seenby mixing a little ferricyanide of potassiumwith ! the liquid
(Gladstone and Tribe, Phil.Mag . Vol. .XLIX.,p.
By electrolysis with a separate current iron is incompletelydeposited as metal from neutral solutions of ferrous salts, someferri c salt being formed. If to the neutral solution of ferroussulphate some ammonium citrate be added containing freecitric acid , and care be taken that free citric acid remains inthe solution, the iron will be deposited in the metallic lustrousform. No iron is separated by electrolysis from a solution offerrocyanide of potassium, but prussian blue appears at thecathode. From the solutions of ferrous oxide in solution of
“
sodium thio-sulphate, all the iron is separated , chiefly as ferroussulphide. From the fluoride of iron dissolved in a solution ofsodium fluoride, metallic iron is deposited (C. Luckow,
Jozcr.
Chem. Soc., Vol. XXXVIII., 1880, p.
c Electrolysis of Ferrous Chloride — Fel l !?
MolecularWeight = 127 According to uAikin
,iron amalgam is .
( 92 )
formed by the action of zinc amalg am on ferrous ch loride ;but accordin g to Damour it cannot be produced in this way
“ D ictionary of Chemistry, Vol. III., p. NVhenzinc amalg am is immersed in a solution of ferrous chloride
,
and a crystal of a nitrate is placed upon it, a black spot isg radually formed upon the surface of the amalgam
,consisting
of reduced iron,which is immediately taken up by the
m rcury. Chlorates and . other sal ts do not produce it
(Runge, Watts’
s Dictionary of Chemistry,”Vol. III.
,p.
The aqueous solution of ferrous chlorid e yields by electrolysis
' chlorine and oxygen at the anode, and iron and hydrog enat the cathode (Watts
’
s“ D ictionary of Chemistry
,Vol. III.
,
p. 37 7 )
Electrolysis of Ferric Ch loride — Fe2010. Molecular
weight = 325 . Ferric chloride is partly reduced to ferrouschloride, partly to metallic iron , by contac t wi th sodium amal
g am and a little water and by contact wi th a.sufficient quant ity of the amalgam i t is reduced to meta l, which remains asi ron amalgam (Cailletet, Watts
’
s“ D ictionary of Chemistry
,
”Vo l.VI.,Wi th magnesium and platinum in contact wi th each otherin a solution of ferric chloride, metallic iron is soon d epositedon the platinum. The passage of a feeble current
,by means
o f platinum electrodes through a simi lar solution, sets free
chlorine at the anode and ferrous chloride at the cathode,but
a stronger one depo si ts metallic iron upon the cathode (Gladstone and Tribe , Phil.Mag ., 4th Series, Vol. XLIX.,
p.E. Becquerel found that when sesquichloride of iron
,
FegCls,was electrolysed , one atom of chlorine and 3
51 atom ofiron are separated for each atom of hydrog en in the voltameter
(Watts’
s D ictionary of Chemistry, Vol. II., p. A concen trated acid solution of ferric chloride yields by electrolysischlorine and a small quantity of oxygen at the anode
,and
ferrous chloride at the cathode (Watt’
s“ D ictionary of Che
mistry, Vol. III., p.I have deposited metallic iron in a reguline state by passin
a current from 15 or 20Smee cells through a solution of sadammoniac, by means of an anode of sheet iron and a cathodeo f copper, for some time , unti l sufficient iron had dissolved.M. Cailletet states that by electrolysing a solution of ferrouschloride mixed wi th sal ammoniac the iron was deposited inthe form of mammillary masses, brittle, brilliant, and hardenough to scratch glass, and the deposi t, when plunged intowater
,evolved numerous bubbles of pure hydrogen. Also
that one volume of the iron absorbed about 240volumes ofhydrogen
,which ignited by contact with a flame and sur
rounded the metal wi th a pale colour (Chem.News,Vol.XXXI.,
p. 1 19 also Jour. Chem. Soc., Vol. XIII , p. According
( 94 )
thickness, brilliant scales of the metal become detached, and
fall to the bottom of the liquid.
Electrolysis of Ferrate of Potassium — I have depositediron from an aqueous solution of this salt
,formed either by
igniting peroxide of iron very strongly for some minutes withc austic potash and saltpetre
,and dissolving the product in
water,or by making a very strong solution of caustic po tash,
immersing in it a large iron or steel anode, and a small coppero r platinum cathod e, and passing a strong current from 1 5 -or
20Smee cells through it until i t acquires a deep amethystineo r purple colour. By that time the cathode had obtained ac oating of iron , ,
which was in the state of a dark powder ifthe powder was too great, but had the appearance of whitec ast iron (or in termediate between that and the appearance ofreguline deposited zinc)when the powder was
‘
sufiicien tly weak.The solution rapidly decomposes, becomes colourless, and
d eposi ts all its metal in the state of peroxide at the bottom ofthe vessel.
Electrolysis of ~ Ferrocyanide of Iron — M. R. Boettinger
d issolves 10 parts of ferrocyanide of potassium and 20 ofsodio—potassic tartrate in 200of water then adds ' a solutiono f three parts of ferric sulphate previously dissolved
' im SO
parts of water, and then , wi th constant stirring,‘ adds drop byd rop a solution o f caustic soda, un til the precipitate -of
Prussian blue is just all redissolved. The resulting solutionmay be used for depositing iron upon cepper (Chem. News ,Vol. XXXVI., p.I have observed that an anode of iron greatly resists the
passage of a current into a solution of perfectly pure potassiccyanide and that if a current of sufficient electromotive forceis employed gas is freely evolved from the iron, and a minute
portion of the metal is dissolved. I have also noticed that ifa very thin wire of silver or gold and one of bright iron beweighed
,then the two twisted together and immersed ' in va
s olution of potassic cyanide contained in a closed bottle,and
set aside for several months, the silver or gold wire has partlyor entirely dissolved, whilst the iron has lost not any ors carcely any of its weight.
(For the electrolytic analysis of compounds of iron, see
Chem. News, Vol. XXXVIII., p. 26 Vol. XLII.,p. 331 Vol.
XLVI , p. 105 and Jour. Chem. Soc., 1 87 7 , Part I., p. 341Vol. XXXVIII., 1880, p. 284 ; Vol. XL 1 88 1 , p. Vol.XLII., 1882, pp. 8 96 and
Separation of Mang anese — Mm. Atomic weight=: 550.
A cation. By the simple immersion of sodium amalgam in anacidulated solution of a salt of manganese, metallic manganeseis deposited and alloys wi th the mercury (Roussin, Chem.News,
( 95 )'
Vol. XIV.,p. 27 ; Watts
’
s“ D ictionary of Chemistry, Vol.
VI., p. According to Phipson , mag nesium deposits man
ganese upon itself by simple immersion in a neutral solutiono f a manganous salt (Proe. Royal Society, 1864, .Vol. XIII.,p. 216 ; Chem. New ,
s Vol. IX. p.Manganese is not deposited ln the metallic state by a sepa
rate current from its neutral or acid solutions, but as hydratedmanganese peroxide.‘ In very dilute solutions of this ! metalcontaining much nitric
,.or 1 a mixture of nitric and sulphuric
acids,permanganic acid is formed , and colours the liquid , (Q.
Luckow, Jour. Chem. Soc., Vol.XXXVIII., p.
Formation of Peroxide of Mang anese. — The electrolysis,by a separate current, of a solution of nitrate or acetate o f
manganese yields a peroxide at the anode (W. 1Vern icke,watts’s “ Di ctionary of Chem1stry,
”Vol VII. p. 899 ,Jour.
Chem. Soc., Vol. IX. p. Solutions of salts of manganese
y ield peroxide at the anode ; one composed of“ one part of
manganese chloride dissolved in eight of water yields, with aplatinum wire cathode, very beautiful alternate rings of purplegreen
,golden yellow, and blue, surrounded by a
0
broad beltof golden yellow. With a solution composed of one part ofacetate of manganese and fifteen of water, one uniform tint isinvariably produced, first golden yellow
,then purple
,then
green (B. Bettger, Pogg.An ia , Vol. L., p.
Electrolysis of Mang anous Fluoride.— Mn.F . Molecularweight = 93 0. I melted some fluoride of manga
2
nese in a plattinum crucible
,and employed two spirals of platinum wire as
electrodes, and a current from six largeS’
mee cells. The conduction was moderate, and
'
gas w as evolved from the anode.In a few minutes both the cathode and the crucible becamequite rotten by the union of the depositedmanganese with t heplatinum. The anode was not corroded. I also -melted thesame salt in a crucible of cepper,
1
and passed the current bymeans of a sheet
’
platinum anode and sheet copper cathode duringhalf an hour. The conduction was free, abundance of g as wasevolved from the anode, but none from the cathode, and itc eased on stepping the current.
“
The/ deposit on the cathodewas black
,and did not evolve h ydrogen with dilute hydro
‘
chloric acid,and was therefore not metallic manganese . The
pruci
gle was much corroded at the line of surface of the
1qu1
I also electrolysed a dilute solution of fluoride of manganeseby a current from six Grove cells and electrodes Of platinum.
Much heat was evolved, gas was set free at the anode, and a
film of black deposit formed upon the cathode. By'
similartreatment of a saturated solution of the salt
,not containing
any free hydrofluoric acid, a film of purple colourwas instantlyformed upon the anode, but it dissolved quickly, and did not
( 93 )
colour the liquid. Gas came from both electrodes freely theliquid also became heated. N0 solid deposit was obtained.
Electrolysis of Mang anous Ch lorid e.— Mn .012. Molecular weight = 126. By the simple immersion of an amalgamof sodium in a saturated aqueous solution of this salt
,Giles
d eposited manganese upon the surface of the amalgam (Phil.Mag ., 4th Series, Vol. XXIV., p. It produces a viscidamalgam of manganese and mercury. According to S. Kern
,
magnesium deposits only manganous oxide (Jour. Chem. Soc.,
1 87 6, Part 2, p.Bunsen filled a porous cell with a hot
,saturated
,aqueous
solution of this salt, placed it in a charcoal crucible containinghydrochlori c acid to the same level
,kept the whole arrange
ment hot, and passed a current from four Bunsen cells fromthe crucible to a platinum wire immersed in the manganoussolution. Metallic manganese was easily and freely depositedbut if the density of the current at the cathode was reducedby any means
,or the concentration of the solution diminished
,
black manganous manganic oxide alone was obtained (TheChemist, No. XL , August, 185 4, p. 685 Watts
’
s“D ictionary
of Chemistry, Vol. II., p.
Electrolysis of Mang anous Sulphate. Magnesium deposited hydrated manganous oxide from a neutralsolution of this salt, but from the same solution acidified itdeposits metallic manganese (Commaille, Chem. News
,Vol.
XIV.,p.
(For the electrolytic analysis of compounds of man g anese,see Jour. Chem. Soc.
,18 7 7 , Part 2, p. 924 , Vol. XXXVIII.,
284,Vol. XLII., 1882, pp. 896, 1320; Chem.News, Vol.
LVI., p.
Deposition of Chromium — Cr. Atomic weight =- 525 . Acation. A slig htly acidified solution of chromic chloride orother chromic salt yields wi th sod ium amalgam an easily decomposable liquid alloy, which, when heated in a stream of
hydrogen or vapour of naphtha, loses its mercury and leavesmetalli c chromium in a spongy state. The liquid turns greenprevious to reduction (Bunge, Watta
’
s“ D ictionary of
Chemistry,”Vol. VI., p. 8 16 ; Roussin , ibid .
,Vol. VI.
,p. 449
Vincent,Phil. Mag ., 4 th Series, Vol. XXIV., p. Mag
nesium precipitates only the hydrated sesquioxide of chromium.
from a solution of chromous and chromic chloride (Commaille,Chem. News, Vol. XIV., p.By means of a current from six Grove cells with platinum
electrodes,I electrolysed a strong solution of fluoride of
chromium containing some free hydrofluoric acid and a littlehydrochloric acid. The liquid soon became hot ; no gas wasliberated at the cathode
,but chlorine and ozone were set free
at the anode,which was not corroded. I also passed a current
( 98 )
platinum wire as electrodes, , and the currentun ng one hour. Conduction Was very free,
much was evolved from the anode, but none fromthe cat ode a bulky deposit quickly formed upon thenegativespiral, especially on the sidetowards the anode. The
deposit weighed 43 66 grains, and consisted of hard jet blackcrystals. Theanodewas not corroded. In a third trial fourGrove cells were e loyed, and a special apparatus devisedand employed to cofiect the evolved gas ; about five cubicinches were obtained. The crystalswere notmetallic uran iumthey were insoluble ln boiling water, but soluble in cold dilutehydrofluoric acid, without evolving gas. About one fourth ofthe de sit consisted of a fine crystalline powder, nearly of
the co oour of copper, but darker, and was composed of thecrystals, witha film of less reduced fluoride u n them ; theyevolved gas in cold nitric acid, or in hot d ute nitric acid.Th ey were not fused by heating alone to redness upon latinum foil, but if causticypotash was added they oxidised. alsoelectrolysed a fused mixture of the pure fluorides of uran iumand potassium with platinum electrodes. The results were verysimilar, except
'
that the deposit upon the cathode fell off asfast as it was formed, and the crystals had to be extracted bydissolving the cooled saline mass in slightly diluted and hothydrochloric acid. They were very much like thoseof silicon ;their form was that of a short pyramid with a square base. Theanodewas very slightly corroded, and made bright by theaction
, and twenty cubic in ches of gas were collected from it.By electrolysis with a separate current uranium is obtained
in small tity only, even from the completely neutral solutio
'
n of the oxide, as a yellowish rey metallic precipitate,soluble in hydrochloric acid (C.Luc ow, Jour. Chem.Soc., Vol.XXXVIII., 1880, p.On passing the current from two elements of a bichromateof tassihm battery through an ueous solution of uraniumace te, formiate or nitrate, brig t yellow uran ium ox ide,Ur,04,was separated at the cathode, and gradually becameblack.
“No uranium remained 1n the solution after the current
had beenpassed two hours. The black compound was uranicuranous oxide, containin 8 1 13 per cent. of uranium (E.F.Smith, Chem News, Vol. 111 , p. 61 , also Jew . Ct ec ,
Vol.XXXVIII., p. 284, Vol. XL., 188 1, p. 3). According tothe same author
,molybdenum, turigsten , vanadium, didymium,
and cerium are not completely precipitated from their solu
tions by the voltaic current.“For the electrolytic analysis of compounds of uranium see
Chem‘
News, Vol.XLII., .p
Separation of Tung sten. -W. Atomi c weight 1 84.
A cation. When tungsten trioxide solutions are reduced by
( 99 )
rz inc, the final product of the action is tungsten dioxide (0.
,Freih, Jowr. Chem. Soc., 1883, Vol. XLIV., p. I 1 fusedsome sod ic tungstate to a clear liquid in a porcelain vessel,and electrolysed it by means of a current from five Smeeelements, a gas carbon anode, and a platinum wire cathode.The conduction wastmoderately free, gas was evolved from theanode
,and at the cathode black matter was set free, floated ,
’difl'
used .in the liquid, andfbecame partly redissolved. According to E. F.Smith, neutral
‘
solutions of the. tungstates are notaffected by thecurrent Vol. XLIII., p. 6
Separation of Vanadium.— Va. Atomi c weight 137.
L. Schicht dissolved vanadium chloride in water containinghydrochlori c acid
,. and electrolysed the solution.
'
No depositiou took place in the blue liquid, the vanadic
p
acid beingmerely reduced to oxide (Chem.News, Vol. XLI., 280
,and
XL II., .p I electrolysed a solution composedpof vanadicacid dissolved in pure dilute hydrofluoric acid, by means of
a current from 10 Smee elements, with a gas carbon anodeand platinum cathode. Gas, having an odour of ozone, was setfree at the anode. I also saturated dilute sulphuric acid withpure vanadate of ammonia
,and electrolysed the solution with
platinum electrodes, and a current from four zinc and platinumelements excited by dilute sulphuric acid. Conduction wasvery s the solution slowly became of a very intensebluish
Ihlac
n
kg ;colour at the cathode
,and a jet black powder of
some thickness was deposited upon it.
(For the electrolytic analysis of vanadium compounds see
f our. Chem. Soc., Vol.
Separation of’ Molybdenum.
— Mo. Atomic weightA cation. Sodium molybdate is not reduced by metallic
tin (Ullik, Watta’
s“ Dictionary
,of Chemistry,
”Vol. V I., p.
From an ammoniacal solution of molybdic anhydride,
by means of a separate current,molybdenum is completely
and firmly deposited upon the cathode as molybdous oxide incoloured rings which thicken and become black. The first blueprec ipitate is molybd ic molybdate, then follow molybdic andmolybd
o
ous oxides. In acid solutions there 18 no deposit. Inammonium molybdate acidified with molybd1c anhydride the
precipitation is incomplete (L.Schicht, Jour. Chem.S .oc Vol.XXXVIII 1880, p. 747 ,
Chem.1News, Vol XLI., p. 280, and
Vol. XLII , p.1' Molybdic acid dissolves freely in pure dilute hydrofluori cacid , evolving a little heat. I electrolysed the solution bothwitli a
,
platinum and with a gas carbon anode and a currentfrom ten large Smee cells. Thecolourless li uid conductedfreely
,becoming instantly of an indigo blue ch
lleur at a pla
tinum cathode. Gas was set free at each electrode that fromthe carbon anode was the most abundant, and had a slightly
11 2
( 190 )
chlorous odour. On stepping the current the deep blue'
filmon the cathode quickly dissolved, and the liquid soon becamecolourless. During the action the cathode was several timesremoved and dipped into water ; much blue matter dissolved,but the water became nearly colourless in half a minute
,even
without stirring,and however large the quantity of the blue
matter was which dissolved it.I also fused some molybdic acid in a porcelain crucible, andpassed a current through it from five Smee elements, bymeansof a g as carbon anod e and platinum cathode. It conductedfreely. The action was rather strong at the anode, but little
gas was set free. No gas was evolved at the cathode, butcrystals quickly collected upon it in a large mass
,which soon
filled the entire solution and 8 read to the anode. The carbonwas not disintegrated or disso ved. The cooled residue was ablack mass of crystals. In a second trial with a current from12 similar cells, and a platinum anode and cathod e, much gaswas set free at the cathode, and less from the anode, and thebluish black deposit formed upon the cathode.A large numberof crystalline needles, from ,th to i th of an inch long
, stoodout at right angles upon the surface of the cathode in the liquid.The deposit imparted a transient green colour to water.Crystals of dioxide of molybdenum,M002, quickly become
.covered with copper when immersed in a solution of cuprics ulphate in contact with zinc (Ullik, Watts
’
s“Dictionary of
Chemistry,”Vol. VI., p.
(F
or the electrolytic analysis of molybdenum compounds seeE. Smith , Chem.News, Vol. XLIII. , p. 6 ; and also Jour.Chem.Soc., Vol. XL., 188 1 , p.
Separation of Lead — Pb. Electroc hemical equivalentEQZ = 103°5. Adyad cation. The deposition of lead by the0.l
simple immersion of zinc in a solution of ni trate or acetate oflead is a very old fact, and when the zinc is in the form of aspiral Wire it constitutes thewell-known lead tree. According to A. Cossa an alkalim solution of plumbic chromate is atonce decomposed by aluminium, with deposition of lead andformation of chromic oxide (Watts
’
s“D ictionary of Chemis
try,
”Vol. VII., p. Thallium deposits lead from a solution of plumbic acetate (W. C.Reid, Chem. News, Vol. XII.,p. Lead in contact With gold in acid or n eutral, cold orhot
,solutions of salts of lead , produces no deposit of lead
(Raoult, Jour. Chem. Soc., Vol. XL, p.
Electrolysis of Plumbic Nitrate.— Pb2NO,. Molecular
w eight= 331. A solution of this salt is slowly decomposed byc ontact w ith aluminium,
and the lead deposited in crystals(A. Cossa, Watts
’
s“ Dictionary of Chemistry
,
”Vol. VII.,
p. Magnesium immersed in a solution of plumbic nitrate
( 102 )
D ictionary of Chemistry, Vol. VII., p. According toBecquerel , if a piece of bright copper in contact with zinc beimmersed in a solution of the chlorides of lead and sodium i tbecomes coated with lead (TheChemist, Vol. V.
,p.
Faraday found that the proportion of lead deposited fromits fused chloride to that of water decomposed by the samecurrent was as 1008 5 to 18 (Watts
’
s“Dictionary of Chemistry
,
”Vol.II., p. According to Buff, solid lead chloride conducts like a metal without decomposition— but rise oftemperature increases its conductivity (Jour. Chem. Soc., 1876,Part I.
,p. Faraday found that by passing a current
through the melted salt chlorine appeared at the anode and
lead at the cathode.
Electrolysis of Plumbate of Potash .— Metallic zinc or tin,
but not iron, becomes coated Wi th lead by simple immersion ina solution formed by dissolving litharge in a boiling hot solution of caustic potash.Haefi
'
elly deposits lead upon copper or brass by immersin gthem in contact with a piece of tin in a hot alkaline solutionof oxide of lead. The tin dissolves in the form of an alkalinestannate
,and the lead is deposited in a spongy state (Chem.
News,Vol. VI.
,p. I connected together a wire of zinc
and one of platinum, and immersed the pair in a solution oflitharge in strong aqueous ammonia ; both wires became coatedwith a black deposit in a few minutes. By contact with air
,
the moist deposit became yellow,and was apparently recon
verted into litharge. F. Weil coats copper, iron, and steelwi th lead
,by dissolving a salt of lead in a strong solution of
potash or soda, and immersing them in the liquid in contactwith zinc ; the deposit, however, contains zinc. To obtain itpure, the piece of zinc is placed in the alkaline lixivium in aporous cell
,and the cell immersed in the lead solution
,the
zinc being connected with the copper, &c., by a wire (Chem.
News, Vol. XIII., p.
Electrolysis of Plumbic Acetate — According to A. Cossa,aluminium slowly deposits lead in crystals from a solution ofthis salt (Watts
’
s D ictionary of Chemistry,”Vol.VII., p.
By a separate current,this solution yields peroxide of lead at
the anode.
Formation of Peroxide of Lead — According to W.Wermcke, an alkalin e solution of the tartrate of lead and sodium,with platinum electrod e and a current from two Daniell cells,yields a black deposit of peroxide of lead upon the anode anda solution of one part of plumbic nitrate and eight of water
gves a similar deposit by such treatment (Jour. Chem. Soc.,01. IX.,
p. 306 Chem.News, Vol. XXII , p.Nobili, in the year 1826, discovered that if a solution of
acetate of lead be electrolysed by means of a ,
large sheet
platinum anode and a platinum wire cathode, a deposit isformed upon the positive plate ; and that if a-polished steelplate be employed as the anode, with a current from four orsix Grove cells, the deposit is in the form of a thin film, andexhibits all the colours of the Spectrum ; and by placing the
positive plate horizontally beneath the vertical negative wirethe colours are in the form of rings, the centre of which isthe wire
,and arearranged in the order of the chromatic scale.
These colours are known as Nobili’s rings. Becquerel, Gass iot and others have, by varying the strength of the batteryand of the solutions employed, and interposing non-conductingpatterns between the anode and cathode, and by using cathodeso f different shapes
,obtained effects of great delicacy and
beauty. Salts of other metals,such as bismuth, silver, nickel,
cobalt, manganese, &c., which yield deposits of peroxide at theanod es
,may be employed instead of those of lead. Becquerel
prepared his plumbic solution as follows — D issolve 200grammes of caustic potash in two quarts of distilled water, add1 50grammes of litharge
,boil the mixture half an hour, allow
it to become clear,take the clear portion and dilute it with its
own bulk of water (The Chemist, Vol. IV.,p. The solu
tion is used cold,and is rapidly deprived of its metal , because
lead is deposited upon the cathode at the same time.By this means may be imparted to polished surfaces of metalsall the richest colours of the rainbow.
“ They commence withs ilver blonde
,and progress onwards to fawn colour, and thence
through various shades of violet to the indigo and blues ; thenthrough pale blue to yellow and orange ; thence through lakeand bluish lake to green and greenish orange and rose orange ;thence through greenish violet and green to reddish yellowand rose lake, which is the highest colour on the chromaticscale (Walker
’
s Electrotype Manipulation,
”Part XL
, l 6thedition , p. Too great a strength of the current covers allthe tints with an uniformly dark brown coating. The deposits,if properly prepared, resist friction well. The process is termedMetallo-chromy.”Metallo ~chromy effected by means of a solution of oxide of
lead in caustic soda, or potash , is largely employed in Naremburg to ornament metallic toys Wagner’s “ Technology
,
”p. 1 17 Bells are similarly colours in Fran ce, and the handsand dials of watches in Swit
Electrolytic Analysis of Compounds of Lead — See Jowr.Chem. Soc.
, Vol. XXXVIII., 1880, p. 284 ; Vol. XLII., 1882,Chem.News
, Vol.XXXV.,p. 264 ; Vol.XLVI ,
p. 106 ;atts
’
s“ D ictionary of Chemistry
,
”Vol.VIII., Part I., p. 7 12,Part
(For eith’
s process for desilvering lead by means of anelectri c current, see Jour. Chem. Soc., 1877 Part XI., pp. 804
( 104 )
and 924 ; Vol. XXXVI., 1879, pp. 288 and 410; and for
Blagden’s process, see Watta’s "D ictionary of Chemistry,
”Vol.VI p.
Separation of Thallium.— Tl. Electro chemical equiva
lent = 204. Amonad cation. Z inc coats itself with metal insolutions of salts of thallium, but tin usually does not. Aocording to Lamy
,zinc precipitates the metal from the solu
tions of the nitrate and sulphate in the form of brilliantcrystalline laminae. I found that crystals of silicon had noreducing effect on a solution of fluoride of thallium containingfree hydrofluoric acid. According to A. Cossa. aluminiumdeposi ts by simple immersion metallic thallium from a solution of thallium chloride at 90° C. (W
'
atts’
s“ Dictionary of
Chemistry,”Vol.VII.
,p.
Solutions of the salts of this metal are easily decomposedby a feeble current, and the metal deposi ted in beautiful crystalline plates upon the cathode. I electrolysed an aqueoussolution of the fluoride by a current from a single Smeeelement, a thallium anod e and a platinum cathod e. It conducted freely, and quickly gave a metallic deposit, in longfeathery crystals, like those of electro deposited tin, but of aless white colour.According to L. Schicht, acidulated solutions of nitrate and
sulphate of thallium were not precipitated by a separate current. From ammoniacal solutions thallium was deposi tedupon the cathod e together with much g as whilst at ‘the anodethere appeared blackish brown thallium oxide much re
sembling peroxide of lead. The current was from fourMeidinger-Pincus elements
,and yielded the metal in a spongy
state and of a dark colour ; but by using only two or threecells, fine permanently adhesive metal was obtained. Fromneutral solutions the metal is imperfectly precipitated onaccount of the acid which is liberated, but in alkaline ones themetal is bright and solid , and the deposition is complete. The(
I
i
i
e
lposit red issolves readily in sulphuric acid (Chem.News, Vol.I., p. 280; also Vol. XLVII., p.
Elec trolysis of Sulphate of Thallium.— T12SO
,. Mole
cular weight= 504. Aluminium immersed in a slightly acidsolution of thallium sulphate becomes coated in ten days withregular octohedra of thallium alum (Watts
’
s“ Dictionary of
Chemistry, Vol. VII., p. A solution of sulphate ofthallium
,ac idulated with sulphuric acid, deposits its metal
upon : zinc by simple immersion (Chem. Newa.Vol. XXXVI.,
. 166)p\
A thallium anode, in water ac idulated .with sulphuric acid,is converted into the black trioxide by a current from two
Bunsen cells (Watta’
s“ Dictionary of Chemistry,
”Vol. VI.,p.‘ i
( 106 )
with and perforated the vessel m a few minutes (The Chemist,New Series, Vol. II., p. I electrolysed a saturated nonacid solution of stannous fluoride by means of large platinum electrodes
,and a current from 10 large Smee cells ;
the conduction was sparing,a little oxygen was evolved
at the anode, and long feathery crystals of tin were slowlyformed upon the cathode. No g as appeared at the cathodeor solid deposit at the anode. By using only one Smee cellthe deposit of tin was white, and beautiful crystals of themetal so on reached across the liquid, and completed themetallic circuit by touching the anode.Also by passing a current from six Grove elements by
means of platinum electrodes through a strong aqueous solution of stannic fluoride containing little or no free
; hydrofluoricacid a grey deposit of tin soon appeared on the cathode. Thec onduction was free, much gas came from the anode, and heatwas evolved in the liquid. The anod e was not corrod ed , nord id it acquire any solid deposit.
Electrolysis of Stannous Ch loride — Sn ag. Molecular
weight = 189. Electrolytic experiments for the separation oftin are usually made with solutions containing this salt.Magnesium deposits stannic acid and s ngy tin from thissolution (Commaille, Chem.News
,Vol. XFV
,p. A “ tin
tree”is produced by immersing a Spiral of zinc wire in ten totwenty ounces of water in which has been dissolved
'
three
drachms of this salt and ten drops of nitric acid , and allowingthe arrangement to remain undisturbed. According toBottger
,sodium amalgam in contact with a concentrated
solution of stannous chloride forms a viscid amalgam. Jouleobtained a beautiful crystalline amalgam by using a separatecurrent and making mercury the cathode in this liquid.I have observed that zinc and lead become tinned by simpleimmersion in a solution of the sal t
,but antimony
,bismuth,
platinum,gold
,silver
,copper
,brass, German s ilver
,nickel
,
iron, and tin do not. According to Raoult, gold or copper incontact with tin in a concentrated and borling solution ofs tannous chloride receive a deposit of tin but gold in contactwith antimony, silver, copper, nickel, i ron, or lead receivesno such coating in either the hot or cold liquid (Chem. News,Vol. XXVI., p. 240, and XXVII., p. 5 9 ; also Jour. Chem.
Soc., Vol. X., p.
Z inc or iron previously coated with a film of metalli c copperby simple immersion process acquire a deposit of tin by simplecontact with a solution composed of one part of crystals ofstannous chloride, two of water, and two of hydrochloric acid(C. Paul, Jour. Chem. Soc., VOL XL , p. Acco rding toRoseleur, zinc and iron become tinned by simple immersion ina boiling hot solution compo sed of one part of fused stannous
( 107 )
chloride,thirty of ammonium alum, and -oi water ; zinc
also acquires a coating of tin by simple contact with a solutionof one part of fused stannous chloride and five of pyrophosphate of sodium, dissolved in 300parts of distilled water.Copper, brass, and bronze become coated with tin by con
tact during a few minutes with that metal in a boiling hots olution of peroxide of tin in caustic potash. F. Weil coatscopper with tin by immersing it, in contact with zinc, in asolution formed by dissolving a salt of tin in a strong solutionof caustic potash or soda, the liquid being at 50
°
to 100°C.;the deposit
,however, contains zinc (Chem. News, Vol. XIII.,
p. Dr. Hillier tins metals by immersing them in contactboth with tin and zinc in a hot solution of one part of stannouschloride dissolved in 20 of water
, to which has next beenadded one or two parts of caustic soda in 20of water.According to Becquerel, copper and iron become tinned byimmersion in contact with zinc in a dilute solution of thedouble chloride of tin and sodium at 160
°
E , but arenot tinned by simple immersion alone in that liquid (The
V., p. For coating iron with tinimmersion in a liquid in contact with zinc Roseleur recom
mends a solution prepared thus z— Take equal weights ofstannous chloride, cream of tartar, and water. D issolve thechloride in one-third of the cold water
,warm the other por
tion of water and dissolve the cream of tartar in it, and mixthe solutions the mixture is clear, and has an acid .
reaction.And a second solution
,composed of six parts of crystal , or four
o f fused stannous chloride,
and 60 of pe phosphate ofpotassium or sodium
,dissolved in parts of distilled
water. The size of the zinc should be about “
Il
a that of theiron. The deposition occupies several hours. When thesolution becomes weak equal weights of the pyrophosphateand fused chloride are added.M. Heeren coats iron with tin by immersing it during two
hours, in contact with zinc, in a solution of two parts oftartaric acid , three of stannous chloride, and three of causticsoda, and 100of water (Jour. Chem. Soc., Vol. XIII., p.Stolba uses a solution of 5 to 10parts of stannous chloridedissolved in 100of water
,and a very minute amount of cream
of tartar added. The metal to be coated is wetted with thesolution whilst in contact with particles of zinc spread over itssurface (Chem. News, Vol. XXIII., p. Brass and copperacquire a coating of tin if placed in contact with that metal ina boiling hot saturated solution of cream of tartar.By means of the single cell process F.Weil coats copper
with tin in a solution of a salt of tin in strong caustic potashor soda. A porous cell
,containing a solution of the 130c or
soda, is placed in the bath, a piece of zinc immersed in i t, thecopper immersed in the hot tinning liquid, and the two metals
( 108 )
connected together by a wire. The deposit is pure tin, andmay be obtained of any thickness. To revive the inner liquid,precipitate the dissolved zinc from i t by addition of solutionof sulphide of sodium (Chem.News, Vol. XIII., p.By means of a separate current, fused stannous chloride
yields tin at the cathode, whilst vapour of stannic chlorideescapes at the anode (Faraday). He found by experiment thatthe proportion by weight of tin deposited from fused stannouschloride
,and of water decomposed by the same current was
as 117 1 6 to 18 (Watts’
s“ D ictionary of Chemistry,
”Vol. II.,p. Iron may be quoted with a beautiful white deposit oftin bymaking it thecathode in a solution of stannate of potash ;but the solution is gradually decomposed by contact with theatmosphere, and deposits peroxide of tin.Various solutions yield tin by this method. Roseleur
’s is
composed of six parts of crystals of stann ous chloride, and
50of pe phosphate of sodium, disso lved in parts of distilled water, the two salts being dissolved in separate portionsof the water, and the so lutions mixed , and then stirred tillclear. It requires a large anode and a strong current. (Forvarious other electrolyticmixtures containin stannous chlorideand other ingredients, see
“The Art of ectro-Metallurgy,
”Longman
’s
“ Text-Books of Science,”pp. 270- 27
Anhydrous stannic chloride did not conduct a current fromcells of W.de laRue
’
s chloride of silverbattery (Bleekrode, Proc. Roy. Soc., Vol. XXV., p.
Separation of Alloys of Copper and Tin — Iron is said toacquire a deposit of bronze by simple immersion in a solutionof 4 to 5 rts of cupric sulphate, 4 to 5 of crystallisedstannous ch oride, and 100 of water.For depositing bronze by a separate current
, Salzede used asolution composed of cupri c chloride, stannous chloride, nitrateof ammonium,
and potassic carbonate and cyan ide,dissolved
in water. For the same purposeNewton used one composedof the tartrates of copper, tin, and potassium.
Formation of Crystals of Tin by Electrolysis — Thecrystallisation of tin is a phenomenon conspicuously strikingunder some conditions in a solution of stann ous chloride. Thecrystals of tin formed upon the cathode increase so rapidly inlength as to grow across the solution, and touch the positivepole in a few minutes. And if the solution and current arestrong and the cathode small, quite a mass of crystals willsoon fill the liquid and converge towards the anode. If the.
anode bedrawn farther away in the solution the crystals followit. The largest crystals are produced by slow action ; to produce them a platinum capsule is covered with an outerof wax
,leaving the bottom uncovered, and then set
,upon a
plate of amalgamated zinc in ,a porcelain vessel. The capsule is
( 1 10 )
carbonate dissolved in aqueous potassic cyanide , with freecyanide added , and using the liquid at about 100
°
F. with acadmium anode.For the electrolytic analysis of compounds of cadmium, see
Jour. Chem. Soc., 187 7 , Part L , p. 340. Also F. Berlste1n , Vol
XXXVI, 1879 , p . 276 and 746 ; Vol. XL.
, 188 1 , p.Vol.XLII., 1882, .8 960. Watts
’
s“D ictionary of Chemistry;
Vol. VII., pp. 22 arid 7 90(E. J. Smith). Chem. News, VolXXXIX., p. 185 n and Jamain), Vol.XL.
, p.'
l09
Vol. XLIII. (E. and V.‘Francken
,
.
p. 106. Jour. XLIL, 1882, p.
Separation of Z inc. Z n. Electra-chemical equivalent
325. A dyad cation. Only the most highly positive
metals usually set free z inc from its solutions. From slightlyacid solutions of z inc salts magn the metal andhydrogen g as (Roussin , Chem. V., .p Ao~
cording to S.Kern ; magnesium evolved hydrogen very slowlyfrom a solution of zinc chloride (Jon/r. Chem. Soc., 1876, PartI,p. Sodium amalgam 1mmersed in a concentrated
solution of zinc sulphate forms a viscid amalg am of zinc
(Bottger,Watta’
s“Dictionary of Chemistry,
”Vol.III. p.Joule also obtained amalga
'
ms of zinc by electrolysis, using acathod e of mercury (ibid . From an alkaline solution of a saltof zinc aluminium easily separates the metal (A.Cossa,Watta
’
s
“ D iction ary of Chemistry,
”Vol. VIL , p. I observedthat in a solution of ei ther n itrate
,chloride
,sulphate, or
acetate of zin c neither antimony, bismuth, platinum, old,
silver, copper, brass, German silver, nickel, iron, tin, l orzinc becomes coated with zinc by simple 1mmersion. I heateda
'mixture of 1 5 grain of crystals of si licon and 1025 gra insof perfectly dry fluoride of zinc in a porcelain crucible to a
full red heat ; the salt was decomposed and zinc set free.According to V. Roque, wrought and cast iron previouslydipped in
'
a strong solution of potassic c arbonate becamecoated with zinc by simple immersion during from three totwelve ho urs in a solution com oecd of parts of water,10of chloride of aluminium, eight of po tassic bitartrate, five ofstannous chloride, four of acid sulphate of aluminium, and fourof chloride of zinc (Chem. News, Vol. XXI. p.Raoult states that gold or copper in contact with zinc, in aconcentrated and boiling solution of chloride or sulphate (butnot nitrate) of zinc, acquires a deposit of zinc. - But gold ln
contact with antimony,silver
,copper
,nickel, iron, or lead , in
cold or boiling acid or neutral solutions of salts of zinc,receives no such coating (Chem. News, Vol. XXVI., p. 240;Vol. XXVIL,
p. 5 9. Jour.Chem.Soc., Vol.XL , p. Copperor brass immersed in contact with zinc in a bo iling saturated
( 1 11 )
solution of chloride of ammcnium acquires in a few minutes aspecular coating of z inc, -
‘but in a s olution of cream of tartarno .such deposit occurs (R. Bottger, Gmelin ’
s Handbook ofChemistry,
”Vols L , p. 50; also Chem. Netes, Vol. XXII.,
p. Copper acquires a fixed and brilliant coating of zincby immersing ~it ~ in contact with zin c in a hot concentratedsolu
tion of po tash or soda (F.Weil, Chem. News, Vol. XIII.,
p. 2By means of ‘ a separate current and az in c an ode
‘
z inc has
been deposited from “
solutions of several 'of its salts, viz., th echloride
,ammonio ch loride, sulphate, ammonio sulphate,
acetate,tartrate
,850. According to Smee, a solution of zinc
oxide in caustic potash is not a good conductor; the zinc anodedoes not readily dissolve in it,"and similarly with potassiotartrate and potassio of cyanide.
Electrolysis of ~ Chloride of . Z ine. Molecularweight = 136. Fused zinc chloride is
‘
reduced to metal bycontact with aluminium (Flavitzky,
'
atts’
s“ D ictionary of
Chemistry, Vol. VIII., Part L , p. It has been statedthat perfectly clean iron acquires a thin coating of zinc bysimple immersion in l a solution of “
30 parts of z inc chlorideand 1 of sal-ammoniac (Watta
’
s D ictionary of Chemistry,”
Vol. VIII., Part IL , p. . According to Grove, nitrideof zinc is formed at an anod e of zinc in a weak solution ofsalo ammoniac (Watta
’
s“D ictionary of Chemistry,
”Vol.°
V.p.
Electrolysis of Sulph ate of,Z inc.
'
— Z n .SO4. Molecular
weight = 161. Sodium amalgam in contact with a strongsolution of this salt forms a visc id amalgam (Bettger). Jouleformed the same compound by making mercury the cathodein that liquid. From a solution of the sulphate, magnesiumdepos its with strong action a mixture of zinc, its hydratedoxide
)and sulphate (Commaille, Chem. News, Vol. XIV.
,
p. 188By means of
'
a current from two Smee cells, with a largezin c anode, a solution of one part of zinc sulphate in five toten parts of Water may b e made to yield a good deposit ofzinc. According to V.. Meyer, pure zinc may be obtainedby the electrolysis of an ammoniacal solution of its sulphatewith a sheet zinc anode and a copper wire cathode (Jour. Chem.
Soc., Vol. X.,2nd Series
,p. 221 see also Watta’s “ D ictionary
of Chemistry, Vol. VII., p.BIM.Person and Sire easily deposited zinc on any metal,
by the separate cu rrent process, with a single cell and a zincan ode, from a solution of one part of oxide of zinc dissolvedin 100parts of water containing 10of alum
"
(Chem.News, Vol.II., p.
11'
s
E lectrolysis of Cyanide of Z inc and Potassium.— A.Wattmakes a mixture composed of twenty gallons of distilled water,200ounces of cyanide of potassium, and eighty by measure ofthe strong est aqueous ammonia. He then fills several largeporous cells with a solution composed of sixteen ounces ofcyanide of potassium to each gallon of water, and partly immerses t hem in the other liquid. In the porous cells he placessheets of copper or iron to act as cathodes, and in the outerliquid clean pieces of zinc to act as anodes, and connects thebattery in the usual way until about sixty ounces of zinc ared issolved , and then stops the current and removes the porousvessels. ‘He next dissolves eighty ounces of carbonate of potass inm ~ in a part of the zinc solution, and returns it to theo riginal portion, and stirs the mixture thoroughly. Af ter thesediment formed has subsided he decants the clear liquidfor use. Articles of iron may be coated in this l iquid.Anodes of zinc are employed , and a little cyanide ofpotassium and liquid ammonia are occasionally added ifn ecessary. The battery preferred is composed of two Bunsenc ells.
Deposition of Alloys of Z inc and Copper.— As early as
the year 1841 M. de Ruolz deposi ted brass,by means of the
battery process, from a solution of the mixed cyanides of .cop
per, zinc, and potassium. One of the best solutions for yielding brass by means of a separate current is that of Morris andPershouse. It is composed of one pound of potassi c cyanide,one of ammonium carbonate, two ounces of cupric cyanide,and one of cyanide of . zinc, dissolved in one gallon of water,and the liquid used at 150
°
F., with a strong current and a
large brass anode. To increase the proportion of copper in thedeposit, either add potassic cyanideor raise the temperature , andto increase that of the zinc, add ammonic carbonate or lowerthe temperature. Walenn recommends a solution composed ofequal parts of ammonic tartrate and potassic cyanide dissolvedin water
,and after addition of the cyanides of copper and of
z inc the oxides of those metals are also added to the solution.If upon trial hydrogen is set free at the cathod e
,a little
ammoniuret of copper is also added to the mixture. There isthen no liberation of hydrogen, and a .deposit of brass may beobtained of any desired thickness. Two or three Smee cellsare sufficient (Chem. News, Vol. XXL , p. 273, Vol. XXII.,pp. 1 and 181 ; Jour. Chem. Soc., Vol.X., p. 103 ; Phil.Mag.,4th Series, Vol. XLI., p. In depositing from an electrobrassing solution, which contains cyanide of potassium andtartrate of ammonium, at a temperature but little above thefreezing point, nearly pure zinc forms upon the cathode
(Walenn , Chem.News, Vol. XXXV., p. 154 ; see also Watta’
s
“ Dictionary of Chemistry, Vol. VII., p.
114 1)
sllve'
r, mercury, copper, lead,
“
thallium, tin , and cadmiumNews, Vol. XIV. p. 2p 7 .) In addition to these
,
ng to Phipson , it deposits nickel, cobalt, and zinc, andeven iron and manganese, from solutions of ferrous and manganous salts ; but it does not deposit aluminium from its
solutions (Watta’
ss“Dictionary of Chemistry,
”Vol.V. p.A sub oxide of magnesium appears to be formed when sodicor ammonic chloride is electrolysed with electrodes of magnesium Wire
,the anode being covered with the black oxide
(W. Beetz,Watts
’
s“D ictionary of Chemistry, Vol. VI.,
p. I have obtained this compound in a great variety.oi If uids by 1mmersing magnesium in contact with platinum
ad ium in them ; solutions of chloride and bromide ofpotassium or sod ium were some of the most suitable liquids
(f roc
iedings Birmingham Philosophical Society, Vol. IV.,
artThe)metal is depomted by means of a separate current.
According to Bertrand, an adherent deposit of the metal maybe obtained by electrolysing durin a few minutes a concentrated aqueous solution of the den le chloride of magnesiumand ammonium by means of a very powerful current and acathode of copper (Chem.News, Vol. XXXIV., p. 227 ; Jou
'
r'
.
Chem. Soc., 187 7 , Part L, p. Bunsen obtain ed it byelectrolysing fused chloride of magn esium at a red heat in adeep and covered porcelain crucible, which was divided bya vertical partition of porous rec laim extending from the
top to half way down the vesse The current employed wasfromten‘
zinc and carbon elements. The electrodes were ofcarbon and were introduced through openings in the cover, andthe cathodewas notched, so that the light melted metal col
more easily obtained by this method if the salt emplo ed con
sists of amixture of four molecules of esic chlori
o
dye, three
of chloride of potassium, and a little 0 oride of ammonium.
In this case, the li uid saltWhghg hter than the magnesium,
the latter falls to e.bottom atts’
s“Dictionary of Chemis
try,”Vol.II. p. 438 ; Vol.For the use of electrolysis in e metallurgy ofsee F.Fischer, Jowr. Chem. Soc., Vol. XLIV.,
1883, p. 399.
Separation of Th orium- Atomic weight=233sets free metallic thoriumfrom fused double chloride of thoriumand tassium in an iron crucible (L.F.Soc., p.
Separation of Norweg ian — Atomic weightAccording .to DraTellef; the sulphate solution of rs
turned ,brown -
ou the"
addition of zinc, and ,the metal is
deposited i n the pulverulent state (Chem. News, Vol. XL.,p.
Separation of Cerium. g Ce. Atomic weightLan thanum. La. Atomic weight= 92. And Didymium. Dy.Atomic weight= 96.— Crude double chloride of cerium andpotassium in a fused state at a red heat is decomposed bymetallic sodium,
and metalli c globules of impure cerium,to
gether with shining scales of an oxychloride of cerium,are
obtained (Wohler, Watts’
s“ D ictionary of Chemistry
,
”Vol.VI., p.When a mixture of oxide of cerium and potassic fluoride is
melted in a porcelain crucible, and subjected to electrolysis,
potassium and silicide of cerium in the form of a brown massare deposited upon the cathode (Ulik, Watta
’
s D ictionary ofChemistry,
”Vol.V.,p. 266 and Vol. VI., p.
According to Bunsen , either of these metals may be separatedby electrolysis with a separate current in the following man
ner z— Its chloride is mixed with sal-ammoniac (both as dry aspossible), and the mixture heated to redness in a platinumcrucible to expel all the sal-ammoniac. A porous clay vesselof the best quality is filled with the residue, then placed in aHessian crucible, surrounded by a cylinder of sheet iron (witha long projecting strip for connection) to serve as the anode,and the space between the two vessels filled with a previouslymelted mixture of an equal number of equivalents of thechlorides of potassium and sodium. A thick iron wire
,enclosed
in a clay pipe,has a coil of very fine iron wire at its extremity
to serve as the cathode, and is immersed in the fused salt inthe inner vessel. The fusion is effected by preference in afire of glowing charcoal, to prevent as far as possible the presence of aqueous vapour, and a strong current is employed(Electrical News, Vol.L , p. 184 see also H illebrand andNorton
'
,
Watta’s “ D ictionary of Chemistry,”Vol.VIII., pp.
T. Schuchardt states that hehas succeeded in obtaining byelectrolysis metallic cerium in globules weighing from four tofive grammes ; .and that he has also by the same process
,with
the aid of a current from six Bunsen cells, obtained metallicdidymium in globules the size of a pea (Chem.News
,Vol. XL.
,
p. Hillebrand and Norton also state that they haveobtained each of these metals by means of electrolysis (Jour.ChemSoc., 1 87 6, Part II., p.According to C.Erk, the electrolysis of a neutral solutionof cerous nitrate by means of a current from three Bunsencells yielded at the cathode a brownish-yellow mass and
,
aquantity of ammonia suflicient to precipitate thewhole of thecerium. A concentrated one of cerous chloride
,
gave freec hlorin e at the anode. and a deposit of ceroso-ceric h ydrate at
the cathode. The same salt in a state of fusion, with amanodeI 2
of gas -
,carbon gave small quantities of metallic cerium, and
reddish white laminae of cerium oxychloride at the cathode ;and at the anode hydrochloric acid was evolved, and a largequantity of ceroso-ceric oxide formed. Strong solutions ofcerous sulphate became yellow at the an ode from formationof ceroso-ceric sulphate, and at the cathode yielded a littlemetallic cerium and a waxy deposit of ceroso-ceric sulphate,which subsequently became crystalline. An aqueous solutionof cerous acetate yielded a basic acetate (Watts
’
s D ictionaryof Chemistry,
”Vol.VII., p.Separation of Gallium — Ga. Atomic weight
Gallium is allied to aluminium and also to mercury. Cad
mium separates ium in the metallic state from a boilingsolution of its ch or1ide by prolonged
'
1mmersion (M. Lewq deBoisbaudran , Jour. Chem. Soc., Vol. XLII., 1882, p So
long as the liquids are sensibly acid, and the evolution ofhydro en goes on actively, zinc does not precipitate either thechlori e or sulphate of gallium ,
but when the liquids becomebasic, and hydrogen rs evolved but slowly, either the oxide ora subsalt of gallium separates in white flakes mixed withsubsalts of zinc (M. Lecoq do Boisbaudran , Chem. News
,
Vol. XXXV., p.On passing a current from five bichromate cells through anammoniacal solution of sulphate of g allium, with latinumelectrodes, metallic gallium is deposited on the cathodh, and a
white film is formed upon the anode. In four and a-half hoursthe metallic deposit weighed °0016 gramme. With ten cells,in five hours i t weighed °0034 gramme. The metal wasadhes ive, not easily burn ished by friction, but better b pressure (Lecoq de Boisbaudran ,
Jour. Chem. Soc., 1876, art L,p. 521 ; Chem.News, Vol.According to Schicht, by electro ysis, gallium,
like zinc,is
deposited completely and in a pure state upon the cathod e
(Chem. News, Vol. XLI., p. By the electrolysis of asolution of oxide of gallium 1n one of caustic tash, by meansof a current from five or six Bunsen’s es and platinumelectrodes
,metallic gallium is deposited as liquid g lobules
(M.Lewq de Boisbaudran , Chem.News, Vol. XXXV., pp. 150and
Separation of Alumin ium.— Al. Electro chemical equiva27 °5
len t=T
A triad cation. Magnesium by simple
immersion in solutions of aluminium salts roduces aluminichydrate (S. Kern , Chem.News, Vol. XXXII ., .p Magnesium does not deposit aluminium as metal from its solutions(Roussin, Chem. News, Vol. XIV , An amalgam ofaluminium is formed by contact of thetmetal with sodium
1 18 )
replaced (The Chemist, New Series, No. 1854,p. By the electrolysis of fused sodic aluminic chloridethe aluminium deposited con tains silic ium derived from the
charcoal electrodes (Deville,Watts’s“ Dictionary of
Vol. L , p. 152, and Vol. V., p.According to A. Bertrand , by means of a separate currentaluminium is deposited on a copper plate in granules fromaluminium ammonium chloride,Whilst chlorine is evolv ed at
the anod e (Jour. Chem. Soc., 187 7 , Part L , p. 16Vol
,XXXIV.
, p. M. Corbelli deposits the metal by ‘
electrolysing a mixture of rock alum, or sulphate of aluminium,
and the chlorides of calcium or of sodium; the anod e beinformed of iron wire coated with an insulating material, anddipping into mercury placed at the bottom of the solution, andthe cathode of zinc immersed in the solution. Aluminium isth en deposited upon the zinc, and the chlorine which iseliminated at the anod e unites with the mercury andforms
)calom
el(Watta
’
s“ Dictionary of Chemistry,
”Vol. L,
1 521)
Thomas and Tilley state that they deposit aluminium froma solution composed of freshly precipitated alumina dissolvedin boiling water containing cyanide of potassium also from a
solution of calcined alum in aqueous cyanide of potassium,
and from several other li uids. They also state that theyhave deposited alloys of a uminium and silver ; aluminium,
silver, and copper ; aluminium and tin aluminium,silver, and '
tin ; aluminium and copper; alumin ium and nickel ; aluminiumand iron, &c. J. B. Thompson says that he has for more thantwo years been depositing aluminium on iron, steel, and othermetals, at a temperature of about 500
°
F.,and also depositing
aluminium bronze of various tints from the pal est yellow to
he richest gold colour (Chem. News,Vol. XXIV., p.
sancon deposi ts the metal from an aqueous solution of adouble salt of aluminium and potassium of specific gravity
at a temperature of 140°
F.,by means of a current
from three Bunsen cells (Telegradphic Journal, Vol. L , p.
T. Ball also deposits i t from the ouble chloride of aluminiumand potass ium (Chem.News
, Vol. V.,p.
I electrolysed a strong solution of aqueous fluoride of
aluminium, containing free hydrofluoric acid, with large sheetlatinum electrodes and a strong current. Gas was evolvedsly from the anode
,and the liquid became heated .
Aluminium used as an anode in dilute sulphuric acid larg elystops the current, probably by becoming coated with a layerof insulating oxide ; but if employed only as a cathode it isnot thus efl
'
scted (Chem. News, Vol. XXXI., p. 99 Telegraphic
Journal, Vol. III., p.It may be superficially co
'
ated W1tli °mercury by being madethe ! cathode
‘
in contact with mercury in acidulated water
1 19
Rendus, XLIV., p, also Watta’sD ictionary of Chemistry,
”Vol.VII.,Aluminium,
like magnesium,has great power m reducing
metallic solutions and depositing their metals by simple‘
im
mersion process ; it reduces those of silver, mercury, copper,lead
,
‘
thallium,and zinc (see.A. Cossa, Watts
’
s“ D ictionary
of Chemistry,”Vol. VII., p.
For the use of electrolysis in the metallurgy of aluminium,
seeF. Fischer,Jour. Chem. Soc., Vol. XLIV.
,1883
, p. 399.For the electrolytic analysis of compounds of aluminium. see
V. Francken , Chem. News, Vol. XLVI., p. 106 ; also Joan ,
Chem. Soc., Vol. XLII., 1882, p. .132 ; and A. Claessen , with ,p. 896.
Separation of Glucinum.— Gl. Atomic weight = 9 °3. A
cation.‘
Nilson and Petterson were unable to separate thismetalby the separate current method (Chem.News, Vol. XXXVII.,p. «Becquerel deposited the pure metal
‘
from a concentrated solution of its chloride by means of a current fromtwenty voltaic cells. It was in the form of brilliant, steelg rey crystalline laminae (Gmelin,
“ Handbook of Chemistry,”
Vol. III., p.For the electrolytic analysis of its compounds
,see A.Claes
sen, Jour. Chem. Soc., Vol. XLII., 1882, p. 8 96.
Separation of Calcium — Os. Atomic weight = 40. According to Klauer, calcium amalgam may be formed either by ,
simple immersion of sodium amalgam in solutions of calciumsalts , or by passing a strong electric current from those liquidsinto mercury. Herschel observed that during the electrolysisof a solution of calcic chloride by means of a separate current,the cathode evolved gas and became coated with caustic lime.- ~ This .metal was first separated by an electric current duringthe year .1808 by Sir ll . Davy, who obtained it as an amalgamby employing a cathode of mercury. Fremy subsequentlyelectrolysed pure calcic fluoride in a fused state in a platinum.
crucible. Brisk efl'
ervescence occurred in the mass,a gas was,
set free at the anode,metallic calcium was deposited upon the
cathode and became converted into lime by the oxygen of theair. -It was difiicult to make the observations, and the cruciblewas soon alloyed and perforated
'
by the action (The Chantal;New Series
, Vol. 1
-Matth iessen electrolysed a fused mixture of two moleculesof calcic and one of strontic chloride with a small amount ofsal-ammoniac in a porcelain crucible. The anode was of . gasCarbon, and the cathode was formed by winding a thin ironwire round a thicker one and dipping its end only just intothe liquid. The calcium was set free as metallic globulesupon t he thin wire. .He states that the metal deposited upon thecathode by a separate current in a fused mixture of chloride
( 120 )
of calcium and the ch lorides of potassium or sodium is notcalcium (Watta
’
s“ Dictionary of Chemistry,
”Vol. L, p.Bunsen deposited calcium in a similar manner to thatemployed for manganese (see paragraph on
“ Separation ofManganese except that he used a greater density of current.He acidulated a concentrated and boiling hot solution of thechloride with hydrochloric acid
,poured the boiling li uid into
the porous cell, and employed as a cathode an ama gamatedplatinum wire. The calcium was deposited as a grey layer uponthe amalgamated surface. The process is difficult, because thecalcium quickly oxidizes to a layer of lime, which covers ~
the
cathode and stops the current. The deposi t must be frequentlyremoved , and the wire freshly amalgamated each time beforere-immersion and even then but a small amount of the metalis obtain ed (The Chemist, New Series, Vol. L , Part II., p. 686,August
,
Separation of Strontium.— Sr. Atomic weight = 87 5 .
A cation. Solutions of salts of strontium are slowly decemposed by simple immersion of metallic magnesium after twod ays they yield a white de sit of strontium hydrate (S.Kern ,Chem. News, Vol. XXXII p. 1 12 Jour. Chem. Soc., 1876,Part L , p. Sodium amalgam decomposed a saturatedsolution of chloride of strontium with formation of strontiumamalgam (Watta
’
s“Dictionary of Chemistry,
”Vol.III., p.886see also Vol. VIII., Part IL , p. Silicon does not separate strontium from heated fluoride of strontium. I heatedto redness a mixtura of the two substances, but no chemicalchange occurred. Caron deposited the metal by fusing itschloride with an alloy of sodium with tin or lead the reduction was not effected by sodium alone (Watts
’
s“Dictionary of
Chemistry, Vol.V., p. Strontium is electro-positive tomagnesium, but not to potassium or sodium,
in water.ir H.Davy was the first to deposit this metal by means of
a separate current. He formed into a cup a pasty mass of
strontium carbonate with water, placed the cup upon a latinum dish, and filled the cup with mercury as the ca ode.
Bypassing a current from 300voltaic cells from the platinum
to t e mercury the strontium was deposited upon and absorbedby the mercury. Hare obtained the metal in a similar manner
(Watta’
s“ D ictionary of Chemistry,
”Vol. V., p.
Bunsen obtained strontium in a precisely similar way tothat of obtaining manganese (see ante), using a salt of strontium instead of one of that metal Watta’s “D ictionary ofChemistry,
”Vol. IL, p. Mat'
essen obtained it fromthef used chloride in the following manner — A small porouscell was placed in a porcelain crucible, and both vessels nearlyfilled with anhydrous chloride of strontium,
the level of thatin the porous cell being the h ighest. The salt was melted so
( 122 )
deposited upon the platinum cathode, and alloyed with ' it.‘By
electrolysing a larger'mass of the salt, with a current from
six Grove cells and a thick platinum wire cathode enclosedwithin, but insulated from a platinum tube, to exclude the
‘
air.
from contact .with the deposi ted lithium, the action was
copious with a old anod e the gold was corrod ed freely, andparticles of it inlarge quantity floated in the liquid and unitedthe electrodes. The cathode swelled greatly, and its lower end '
bent itself towards the anode, became quite grey in colour, andsp lit in the direction of its length.Bunsen was the first person who electro-deposited this metal
(Watta’
s“Dictionary of Chemistry,
”Vol. III., p. 7 By,
electrolysing fused chloride of lithium with a current fromfour or six Bunsen cells, an anode
'
oi gas coke, and a cathodeof iron wire, be deposited silver white metal upon the wire
,
(Watts’
s“D ictionary of Chemist Vol. II., p. Schnitzler
also electrolysed a mixture of t e fused chlorides of lithiumand ammonium by a curren t from twelve Bunsen cells
,and a
.
cathode of iron wire,and obtained ametallic lithium (Jour.Chem.
Soc.,Vol.XXIL, p.
Separation of Sodium.— Na. Electroc hemical equivalent
Amonad cation. In a solution of sod ic chloride, magnesium evolves hydrogen alewl sodium hydroxide beingformed, rendering the solution al aline (S. Kern,Soc., 1 87 6, Part L, p. Beetz observed that under theseconditions a black suboxide ofmagnesium is formed. Carbon,also iron, reduces the melted hydrate or carbonate of sodium
'
at a high temperature , and sets free the metal.Sir H. Davy first electro-deposited sodium in the year 1807by moistening its hydrate with water in a platinum capsulewhich acted as the anode, dipping a platinum wire cathode inthe salt, and using a current from a battery composed of 100to 200cells. He also deposited it more eas ily into mercury .
in a simi lar way to that already described under magnesium,
and thus obtained an amalgam of the two metals.In the electrolysis of melte d sodic hydrate an anode oi
either platinum, silver, or copper dissolves in the liquid , and
the respective metals are deposited upon the cathode (A.Brester, Chem.News, Vol.XVIl., p.
Electrolysis of Sodie Fluoride.— Na.F. Molecular weightx 42. I have noticed that crystals of silicon thrown in tomelted fluoride of . sodium evolved bubbles of vapour, whichexploded and burned with a yellow flame on arriving at thesurface of the liquid. In a second trial, 7 grains of the dryfluoride in powder mixed with one grain of the crystals werehbated to redness ; the crystals lost
°l 5 grain in weight. I
electrolysed a saturated a queous so lution of sodic fluoride by r
a curren t from‘
s ix Grove c ells with platinum: electrodes ; gas
123
was evolved from the anode, and emitted a powerful odour‘
of ozone.‘
Electrolysis of Sodie Chloride.— Na.Cl. Molecular weight5 8 5 . Hisinger and Berzelius electrolysed a solution '
of common salt with silver electrodes. Gas was evolved s
at
the cathode,and after a time at the anode also. The anode
became covered with argentic chloride,the liquid n ear it ' eon
tained dissolved chlorine,and the solution near the cathode“
contained free soda. With lead electrodes the negative wireevolved g as , and received a deposit of crystals of lead, and theanode became coated with plumbic chloride. By electrolysinga solution of common salt
,Higgins and Draper observed that '
chlorine was set free at the anode,and hydrogen gas and soda
at the cathode. But if the cathode consisted of mercurysodium amalgam was
‘produced. According to Matthiessen ,a fused mixture of the chlorides of calcium and of sodiumyields a deposit of the latter metal
,when electrolysed in a
certain manner (Watta’
s“D ictionary of Chemistry,
”p. 7 i 5)
Electrolysis of Sod ium Carbonates. -Na200
3and Na
HCOa. According to Favre and Roche, by electrolysis, neutral
sodium carbonate Splits up into CNa.O3and Na, the sodium
being oxidized by the water with separation of hydrogen.The acid carbonate is resolved into Na and CH0 the sodiumbeing then oxidized and hydrogen evolved ; the 2CHO3 isthen resolved into 2CQ
z +H20+O. According to Burckhard;
sodic carbonate in a state of fusion is a good conductor, and isdecomposed by electrolysis into carbonic acid at the anode,and soda tog ether with a little carbon at the cathode (Chem;News
,Vol.XXL , p.
Electrolysis of Biborate of Sodium — Fused borax yieldsoxygen gas at the anode and boron at the cathode. ,
The
boron is separated by indirect action the current resolves thesoda into oxygen and sodium, and the latter separates boronfrom the boracic acid (Faraday, Gmelin
’
s“ Handbook of Che
mistry,”Vol. L ,
p. Burckhard states that fused boraxconducts
,suffers electrolysis, and a series of compounds are
formed or volatilised but the chief result is that the salt is decomposed into sod a and boron at the cathode and oxygen at
the anode (Chem.News, Vol. XXL , p.
‘
Electrolysis of Sodie Sulphate. Na2804. Molecular
weight= 140. By the electrolysis of this salt in a fused statewith platinum electrodes, sodium is deposited and combineswith thec athode (Brester, Chem.News, Vol. XVIII., p. z
1,From the results obtained ; by electrolysing sulphide ' of
sodium. Bufl'
‘concluded that all the sulphur travelled ,to
124
the anod e and the sodium towards the cathode (Chem.News,Vol. XV., p.
Electrolysis of Diphosphate of Sodium — Na EPOP .Asolution of this substance is decomposed by a separate currentinto phosphoric acid at the anode and soda at the cathode.According to Faraday, acid phosphate of sodium in a state offusion yields hydrogen at the cathode (Gmelin,
“ Handbookof Chemistry, Vol. L , p. According to Burckhard , fusedpyrophosphate of sodium
,electrolysed with platinum elec
trod es, yields ~
phosphide of platinum ; but the chief result isthat the salt splits up into oxygen , phosphorus, and soda
(Chem. News, Vol. XXL, p.For the reducing action of sodium amalgam on solutions of
silver,mercury, iron, and chromium, see the sections relatin
gto these metals also Watts
’
s“ D ictionary of Chemistry,
Vol. VI., p. 8 16. For Jablochkofi'
s process of making sodiumby electrolysis
,seeScientificAmerican, Sept. 22, 1 883, p. 643.
Separation of Potassium — K. Electroc hemical equiva
lent= Amonad cation. Magnesium,by simple immer
sion in a solution of potassic dichromate, forms potassichydroxide (S. Kern, Joar. Chem. Soc., 187 6, Part II., p. 47Z inc amalgam immersed in a solution of caus tic tash liberates pure hydrogen (Watta
’
s“ Dictionary of Chemistry,”
Vol. III., p. Acco rding to W. Skey, an aqueous solution of po tassic chloride becomes alkaline by contact eitherwith zinc or with silver
,in the first case, probably by decem
position of water and formation of ammonia, aided by formation of zinc oxid e, and in the second by oxidation of thesilver by free oxygen, and the subsequent decomposition ofthat oxide with formation of silver chloride and causticpotash (Jour. Chem. Soc., 1876, Part II., p. Both carbonand iron separate potassium from melted po tash at a whiteheat, and the process for obtaining potassium is based uponthis fact. Brester states that even silver will dissolve in largequantities in melted potassic hydrate (Chem.News
,VOLXVIII.,
p. and I have observed that when this hydrate is meltedin a pure silver crucible the vessel loses in weight.
Elec trolysis of Potas sic Hydrate. KHO. Molecularwei h t= 5 6 °1. Potassium was first separated by electrolysisin t 0 year 1807 by Sir H. Davy. He moistened a piece ofpotassic hydrate with water, placed it in a platinum ca ule,which acted as a cathode, and touched the hydrate with
) 8
the
platinum wire anode of a battery of from 100to 200of Wolaston’s cells. The potash liquefied , and globules of the metalseparated at the cathode. Since that time it has been foundthat even a feeble voltaic current will liberate potassium fromaqueous solutions of some of its salts, and if the deposited
( 12s )
evolved, and violent electrolytic action occurred ; nearly whitehot metallic globules also accumulated and exploded « re
peatedly. The end of the anode fused,and particles of
platinum ramified from i t in white hot threads, and a shortelectric are (about 1-loth of an inch in length) was produced.I also perfected and used a somewhat elaborate platinum
apparatus, by means of which the gas from the anode wasprevented from coming in contact with the cathode
,and
might be collected, the electrodes being enclosed within (butisolated from) two wide platinum tubes. One thousandgrains of the perfectly pure salt were electrolysed in thisapparatus by mean s of a current from six Grove cells. Theanode, which was a solid rod of platinum
,was rapidly cor
roded , and was thus cut off at the level of the liquid andstopped the current the corroded surface was very bright
,as
if fused po tassium was deposited upon the cathode. Muchspongy p latinum was diffused in the melted salt
,and the
apparatus was a little corroded at the surface of the liquid.No gas was evolved at the anode. The deposited potassiumdid not alloy with the stout rod of platinum used as thecathode. grains of g rey metallic platinum were foundin the saline mass a salt of platinum appeared to have beenformed at the anode, then dissolved or diffused throughoutthe liquid and decomposed by the heat, and thus the liberatedfluorine did not escape at the anode, but was evolved in themass of the liquid genera lly, and came into contact with theliberated potassium.
Having ascertained the electri cal relations of palladium,
g old , platinum,and irid ium in the fluoride, palladium being
the most positive and iridium the most negative, I repeatedthe experiments with an anode of iridium and a current fromth ree Grove cells. Cepious clouds descended at once fromthe anode, and made the liquid opaque ; there was also aviolent action at the anode. The anod e became black, and alittle gas was evolved from it, accompanied by an acid odourlike that of a mixture of sulphurous anhydride and hydrofluoric acid. Potassium was freely liberated at the cathode,and produced occasional e lesions. With a current fromsix cells the anode dissolv rapidly, and soon lost thirtyeight rain s. I then put a pure gold anod e, and employedtwo ce 3. Gas, of a feebly acid odour, was freely evolved atthe anode and with a current from six cells was very copious,and smelt much like sul hurous anhydride. The gold dis~
solved much less rapidly the iridium. With a palladiumanode and a current from six cells the anod e rapidly dissolved,potassium was deposited and exploded frequently, and anodour like that of hydrofluoric acid was strong, much gasbeing liberated ; 333 grains of free metal were found in thesalimmass. The platinum cathodewas not corroded .
In the experiments the platinum anode d issolved, as ifmelted ; the iridium one was black, the palladium one wasoxidised of various colours. The platinum vessel was cutinto at the level of the surface of the liquid , evidently notby the fused fluoride of potassium, but by some substance setfree at the anode by electrolysis. In another instance I electrolysed the pure fused fluoride
'
with a large platinum anode, smallplatinum cathode
,and a current from three Grove cells during
half an hour. Much gas, having an odour . of ozone and hydrofluoric acid , was evolved from the anode, and the latter dissolved rapidly and lost 375 grains in weight. The gasreddened test paper. The platinum containing vessel wascorroded at the line of surface of the liquid, and lost abouteleven grains. About fifty-one grains of free metallic platinumin loose powder were found in the saline residue. Each ofthese experiments shows that a very corrosive substance wasliberated at the anode.I electrolysed the fused salt with a gas carbon anode and
a platinum wire flat helix as a cathode with a current fromsix Smee cells. Free conduction occurred, and much gas wasset free from the anode only. The part of the anode in theliquid was not visibly corroded.I also electrolysed about 80z . of pure double fluoride of
hydrogen and potassium KFHF) in a fused state during halfan hour
,at about 300° with a current from ten Smee
cells,and electrodes of stout sheet platinum. There was
cepious conduction, and abundance of hydrogen evolved atthe cathode
,but no gas from the an ode, which was rapidly
corroded away, with a rough surface , and lost grains.The salt became less fusible by loss of hydrofluoric acid
,which
escaped freely all the time. The saline residue contained a
small amount of dissolved platinum salt, and nearly 9 grainsof free metallic platinum: In a second experiment
,lastin
half an hour, the salt was kept only just fused, and a amagg old anode was employed . The conduction was free
,and
much gas was evolved from the cathode, and a film of brighty ellow gold spread over the surface of the salt
,and connected
the electrodes,unless the liquid was continually stirred. The
anod e rapidly dissolved (more quickly than that of platinum),and the salt of gold at once decomposed, and set free finelyd ivided gold as a dull, red-brown powder at the anode. Noappeared at the anode at any time that from the cathode
etonated on applying a light. There was loose red-brownpowder of gold, weighing 1 °4
'
grain, upon the cathode, but ofadherent gold only °O5 grain. The anode was corroded
,and
lost 68 0grains. The saline residue contained no dissolved gold '
;
bult ‘85. grains of red -brown powder, containing 530grains ofgo
In a. third similar experiment, b y using a large sheet
( 128 )
platinum anode and a small platinum cathod e, and a currentfrom ten Smee cells during two hours
,the phenomena were
the same as in previous experiments. The anode lost 28grains ; much loose platinum collected on the cathode, whichwas neither corroded nor alloyed. The saline residue confained a trace of dissolved platinum salt, and nearly all thecorroded platinum in a metallic state. In a fourth experimentI continued the action during three and a-half hours the re
sults were as before. The loss of the anode was 35 7 3 grains.The saline residue contained a small quantity of dissolveddouble fluoride of platinum and potassium,
which,after being
well washed, was dried and heated to redness ; it then shotabout as if gas was evolved from it. In a fifth similar ex
periment, lasting four and a-half hours, at the lowest possiblefusion temperature, more of the brown platinum salt formedat the anod e and dissolved in the liquid. The anod e lost
grains. In a last experiment I electrolysed a gentlyfused mixture of 900 g rains of the pure double salt and100grains of pure argentic fluoride, with a large anode ofplatinum and a large cathode of silver. Conduction was
complete with ten Smee cells. No gas was evolved at eitherelectrode. The surface of the an od e disintegrated rapidlyand lost 49 84 grain s in four and a-half hours ’ action. The
separated platinum d issolved only to a small extent in theliquid
,andpsubsided in admixture with the silver to the bottom
of the vessel as a fine, black powder, weighing 73 93 grains,which lost less than two per cent. when heated to redness.Some grey silver powder was deposited upon the cathode. Inall these experiments with the acid fluoride, saline films con
tinually formed upon the surface of the liquid. They camefrom the cathodep and were more abundant the deeper thecathodewas immersed.I electrolysed a nearly saturated aqueous solution of pure
fluoride of potassium by means of a current from six Grovecells with large platinum electrodes. Conduction was copious,and the liquid acquired a nearly boiling temperature. Muchgas, having an odour like that of a mixture of ozone and
chlorine, was evolved at the anode. A saturated soluti on ofthe same salt, electrolysed by a current from ten large Smeecells with large platinum electrodes, evolved as at each electrod e. That from the anode smelt powerful y of ozone, andreinflamed a red hot splint. Several other experiments withvariations in the size of the electrodes were made, and withaddition of hydrofluoric acid, but the results were similar.I saturated some pure dilute hydrofluori c acid of 40percent. at 60
°
F. with pure double fluoride of hydrogen andpotassium, and electrolysed the solution by a current from tenSmee cells, a gold anod e, and a platinum cathode, during 5 §hours. Gas was evolved freely from both electrodes, and a
( 130 )
solution of potassic cyanide, Kolbe observed that potassiccyanate was formed at the anod e (Watta
’
s“ D ictionary of
Chemistry,”Vol. II., p. Faraday noticed that the aqueous
solution yielded by electrolysis hydrogen and potash at thecathode
,but no oxygen at the anode ; that the liquid around
the anode became brown , that the fused salt, and that aqueoussolutions of potassic sulphocyanide and ferrocyanide behavedsimilarly (Gmelin
’
s“ Handbook of Chemistry,
”Vol. I., p.Electrolysis of Potassic Ferrocyanide.— RFCy. Mole
cularweight = 368. When s solution of ferrocyanide of potassium is decomposed by an electric current, ferrocyanide ofpotassium is formed at the anode, and hydrogen and potashappear at the cathode (Watts
’
s“ Dictionary of Chemistry,
Vol. II., p. The alkaline ferrocyanides yield alkali atthe cathode, and hydrocyanic acid and Prussian blue at theanode, unless the anod e is composed of copper, in which casea deposit is there formed of cyanide of copper (Porrett, ibidp. 222)
Electrolysis of Potassic Ferrideyanide.— KFdCy. Molecular weight = 329. Carbon charged with hydrogen easil
reduces a solution of ferri to ferro cyanide of potass ium (Glad)i
stone and Tribe, Jour. Chem. Soc., Vol.XXXIII., 18 78 , p. 309A platinum hydrogen couple does the same readily (ibid.Bottger observed a similar effect with palladium contain ingoccluded hydrogen.When a solution of po tassic ferri cyanide is electrolysed by a
se arate current yellow prussiate is formed upon the cath ode
(Watts’s “D ictionary of Chemistry, Vol. II., p.
Separation of Rubid ium.— Eh. Atomic weight = 85 °48.
Amonad cation. Like sodium and potassium, this metal isseparated from its fused carbonate at a white heat by simplecontact with carbon. It was first obtained by electrolys ingits fused chloride with a graphite anod e and a cathode of ironwire. It has been obtained by electrolysing a fused mixtureof the chlorides of rubidium and calcium in their equivalentproportions at a temperature a little below redness. It is alsoobtained as an amalgam by electrolysing a strong neutralaqueous solution of rubidium chloride with an anode of pla~tinum and a cathode of mercury. The metal itself is decidedlymore electro-pos itive than potassium, and both it and itsamalgam decompose water readily (Wette’e “ Dictionary ofChemistry,
”Vol. V., p.
Separation of Caesium.— Os. Atomic weight = 132°66. A
monad cation. Unlike rubidium, potassium, and sodium,this
metal is not liberated from its fused carbonate by contact withcarbon at a white heat. An amalgam of the metal may be
( 131 )
easily obtained by electrolysing a solution of caesium chloridewith a cathode of mercury (Watta
’
s“Dictionary of Chemistry,
”Vol.L , p. ~M. Setterberg obtained metallic caesiumby electrolysing a dry mixture of four parts of caesiumcyanide and one of barium cyanide. This mixture fuses moreeasily than caesium cyanide alone (Chem. News, Vol. XLV.,
p. 94, and Vol. XLVI., p.
Separation of Ammonium E4N1,and Electrolysis of
Ammonia — HEN. Weyl , in 1864, discovered that sodium
swells , liquefies, and dissolves in anhydrous ammonia liquefiedby pressure, and on removal of the pressure the sodium returnsto the metallic state ; also that potassium behaves similarly ;that barium forms a deep blue liquid with a metallic lustreand that silver
,mercury
,copper
,and zinc likewise form un
stable compounds with the liquefied gas (Watts’
s“ D ictionary
of Chemistry,”Vol. V., pp. 328 Seeley in 1870 sabse
quently discovered that metallic rubidium,potassium, sodium,
or lithium, by simple immersion in colourless anhydrousammon ia liquefied by pressure, dissolved in the liquid, and
produced intensely blue solutions of powerft reducing pro
perties (Chem.News, Vol. XXIII., p. 169 Watta’
s“ Dictionary
of Chemistry,
”Vol. VI., p. I have also verified theseresults, and have examined the action of the sodium solutionupon various compounds (Proc. Roy. Soc., Vol. XXL , 1873,pp. 140, In all these blue solutions i t is supposed thatammonium is set free and dissolved.Bleekrode ascertained that anhydrous liquefied ammoniawasa conductor and an electrolyte. He passed the current from80Bunsen cells through it ; gas was evolved, and the liquidbecame intensely blue. He also passed the current fromcells of De la Rue’s chloride of silver battery through theliquid by mean s of platinum wire el ectrodes. The anodebecame black, much gas was evolved, and the liquid becameintensely blue. On stopping the current the colour disapeared . In these experiments ammonium was probably set
ree and dissolved,and produced the colour.
Damp iron filings exposed to the air or to nitrogen inducethe formation of ammonia (Berzelius).
Electrolysis of Aqueous Ammonia — By simple immersionof magnesium in solutions of ammonium salts, ammonia andn itrogen are set free (S. Kern ,
Jowr. Chem. Soc.,1876, Part II.,
p. 47 By electrolysis of ammonium salts ammonia is produced at the cathode (C. Luckow, Jour. Chem. Soc., Vol.XXXVIII., 1880
,p. According to E isinger and
Berzelius a concentrated aqueous solution of ammon ia con
ducts as imperfectly as pure water, but by addition of a littleammonic sulphate it is rendered easily decomposable. A goldanode becomes covered with amber coloured fulminate of the
x 2
( 132 )
metal and dissolves, and the cathode is gilded.”With a
mixture of one volume bf strong aqueous ammonia and threeof water, oxygen is set free at the anode, and the anodebecomes corrod ed. With a cathode of mercury, the bulkyamalgam of ammonium is obtained (Gmelin
’
s Handbookof Chemistry,
”Vol. L,p.
According to Favre, under the influence of the current,ammonic oxide is decomposed thus z— l st, 3
(NH4)2+03. The three equivalents of ammonrum set atliberty decompose the water, like potassium or sodium,
thus— 2nd
,3 NE
4)2+ 3 H20= 3 (NH 20+ 3 H2. The Oxygen of
equation 0. 1 , reacting upon the ammonium,gives — 3rd ,
The first equation represents the electrolysis preper (Joar. Chem. Soc., Vol. IX.,
p.The se-called “ ammonium amalgam with mercury was discovered in 1800simultaneously by Seebeck in Jena
,and by
Berzelius and Pontin at Stockholm. It is obtained either bythe contact of sodium amalgam with strong solution of certainsalts of ammonia, or by the electrolysis of a concentrated solution of sal-ammoniac, or. certain other ammoniacal salts (notthenitrate) with a cathode ofmercury. In each case the mercuryswells to a bulky mass
,which on the cessation of electrolysis
spontaneously decomposes into liquid mercury and a mixtureof two volumes of ammonia and one of hydrogen. It solidifiesbelow 0
°
C., and crystallises in cubes. It does not decomposebelow 29
°
C. if previously frozen. In the separate curren tprocess oxygen is evolved at the anode
,if the salt employed is
aqueous ammonia, or the carbonate, sulphate,or phosphate
,
but chlorine if it is cal-ammoniac,and but little gas is set free
at the cathod e (Watta’
s“ D ictionary of Chemistry,
”Vol. L ,p. If the cathode cons ists of s ongy platinum impregnated with mercury
,much as is evo ved
,and no amalgam 18
formed (Wetherill, ibid ., Vo VL, p. A concentratedsolution of trimethylamine hydrochloride behaves with sodiumamalgam just like one of cal-ammon iac (Pfeil and Lippmann,Watta’s Dictionary of Chemistry,
”Vol.VL,p. Various
investigators cons ider the ammoniacal amalgam to be merely aspongy mixtu re of mercury and hydrogen (see SeeleyNews, 187 1 , Vol. XXIIL, p. 169 ; also Pfeil and Lippmann,Watts
’
s“ D ictionary of Chemistry, Vol. VI., p.
Electrolysis of Nitrate of Ammonia — NH4NO
3. Mole
cular weight= 80. The action of a copper zinc couple on asolution of ammonium nitrate showed that both nitrate andammonia were produced. In the cold the nitrate , even in a
solution of 20 per cent , was completely reduced to ammoniain about 24 hours, without the escape of ammonia, free orcombined (Gladstone and Tribe, Jour. Chem. Soc., 187 8, Vol.
XXXIII.,p.
( 134 )
Electrolysis of Sulph ate of Ammonium. -Am Molecularweight = 132. A solution of ammonic sult ate l s decemposed by the current, acid and oxygen appearing at the anode,alkali and hydrogen at the cathode (Sir H.Davy). With ironwire electrodes, hydrogen and free ammonia appear at thecathode, and at the anode oxygen is evolved, but not untilafter some time ; persulphate of also (Hisingerand Berzelius).
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— Further Pract ic al App lication of Tran s formers .
Op ini ons of th e Press on Vol. II.
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