Manufacture of S~gar of Lead. 105

will sometimes happen that the quantity put in is douhled~hieh:I find is of no injuri'ohs consequence witli this mixturej butm{~ht en- danger the person firing with the fulminating mercury, as t~e~,cap wilt burst too violently." : " :

With respect to the power of igniting the charge, the different kinds of powder which I have compared are equally effectual.

IV. I-submitted the mixture of chlorate-of l~otash mentioned above to the following experiments.

1. That part only ignited which was struck9 without igniting that lyin~ around it.

~. In the fire it burns away with noise. 3. I placed it in the usual way in copper caps, but could not ig-

nite a charge with them. The cause of this may be explained by the construction of the locks, with reference to the properties of this detonating powder. That part of the cap situated just above the opening ot" the cylinder remains, as the blow cannot fall on it unig- nited, as shown by the experiment No. 1. But the communication of the ignited part with the charge, is prevented by the manner in which t|le cock strikes the cap. In guns in which such powder is used for igniting, it lies as above stated, in small balls in a conical aperture. Hero it is nearly all ignited by the striking of the cock, and must of necessity flow inwards, every other wayofescape being shu~ up.

In conclusion , ~ I have to add that the method of filling the caps recommended by Mr. ~Vri~ht is not only laborious, but even dan- gerous. ~ How are manufacturers to eml~loy that method when they have to fill several thousands a week? I have made various t~ials, and the followin~ process seems to me to be the best.

Pour some adffesive solution or tincture over the powder, and mix it into a stiff" kind of liquid. Take with a brush or a stick a large drop of it, and appl,¢ it against the bottom of the cap.

T . . . . his method is both quick and free from danger; whilst on filling with the dry detonatinff powder, the least careless totteh may pro- duce an exl~losion.

In order to prevent the corrosion of the cylinder, and its beeom. ing useless bv the formation of sulphuret of iron (an evil very ecru-

on with iron touch-holes, and caused more by the action of the gun-.powder than by that of the igniting substance,).the inside, ofthe cyhnder should be lined with a metal which will neither oxidaten0r easily combine with the ingredients of the powdei-.~[Ph//os. ~ o

Manufacture of Sugar of Lead. Tins salt is art object of considerable interest on account of the

great use made of it in caliCo-priuting~ as well as in some other arts; In the calico-nrintin~, business, it is in reality one of the ,most U~,/ll preparations;~r according to the French term. which m a n y ~ the English writers wish t o ~aturalize among us, mordant, or biter-in.

VoL l l I . ~ N o . ~.~F~gnRVArtv, 18~9. 14

106 M a ~ c l u r e of ,S;u~'ar of Lead.

It is probable tl at in time it will be less used than at present; an(1 that acetate of lime, which is a much cheaper salt, and which also de- composes alum, and cJ~anges its base into an acetate, will be pre- ferred.

The French complain much that this change is likely to take place; because the manufacture of sugar of lead brings into use the inferior wines produced in some of their provinces, especially those Which ~ii~1 not keep for any t~me: but as a greater consumption Ms taken i:,aee, and tile pyroligneo1~5 acid, or vinegar of wood, presents greater ~.dvantage% these two products are become reciprocal advantages.

Formerly this acetate of" lead was made from vinegar and blue lead: that is to say, commot~ metallic lead: some manufacturers, however: used white lead for this purpose; but as this is usually mixed with more or les~ whiting, a portion of the acid was takenup by this calcareous earth; the acetate of lime thus produced~ augment- ed ~he quantity of mother water, and was injurious to the crystalli- zation.

' l r he process former y used was this; as the lead is no~ attacked by the acid while it retains its metallic form, cast lead was cut in pieces by chisels, f'or milled lead was considered as too close; these cut- tings were put into pan% and a small quantity of vinegar was poured on them, btit not sufficient to cover them. The part which was not sunk beneath the acid becomes oxidized in a short time; and as the cuttings were stirred several times a day, in order to change the sur- faces exposed to the air or to the acid, the oxide was gradually dis- solved in the vinegar. When the acid was saturated~ the liquors in the several pots were poured into a tinned copper boiler, and boiled down one-third ; the liquor was then filtered, and boiled down again, until on trial it appeared fit for crystallizing; it was then decanted aud set by to crystallize ; the first crop was large.nod white needle- like crystals ; but the mother waters, by further cv~p~ration~ yielded coloured crystals.

This method has given place t9 another, which is far superior~ aud founded upon ~n exact knowledge of the nature and proportion of this salt.

I t is welI ~tlown that, according to the best analysis, the acetate of lead is composed in round m~mbers of 58 parts , in 100 oxid~ of lead, ~6 of acid~and 16 of water~ of course, th'e saturating power of, 'the pyroligneous acid intended to be employed must be ~amined, in order to determine how much of it answers to 9~6 parts of the dff acid. When this acid is at 40 degrees of the acidemeter, it ~enerally requires 68 lbs. of it to be pouretl on 68 lbs. of litharze. '~'he solu- tion takes place immediately, and is"s~ qu{ckly ma~e, that a con- ~iderable heat is produced, ~vhich:::t;et~in~.~tkesu'gar of lead in solu-

:tion ; bat a little fire is usually .given; a~d ~ m e water added, t0 :~eep up this solution until the liqubr ha~.bebome clean, and it is thelx~6ured, into er~cstaltizing pans.:i . !~;~ i ~:.."

"l~h~crystals, which usually weigh g~ ~!l~s::are t~roduced in about ~hirty:si~::hours; they are drainedk~c~i~.efully dr'led The mother w a t e r , whichcontalns about eh'i;lb~.~f~ the.. ;ugar, by evaporation

TREaDWELL O~ tl~e use o f CastIron: ~.e.: , 107

:yields great part of its contents; but the crystMs are by:no~ m~ns so fine as the former, When the mother waters no longerylel~i c~s~: tals, they are mixed with salts of soda, when a carbonate.0flead falls down, ~md a~etate of soda remains in solution. The c~irbonate of lead may be used itlstead of litharge in ftlture operations. •

It will be found preferable at first to add the mother water to the acid and litharge, and thus near 100 lbs. of good sugar of lead will be obtained instead of 75 lbs. by the first crystalliza~on ; but this method cannot be continued for any time, as tile liquor will become greasy, the crystallization will be hindered, and the sugar of lead becomes difficult to drain, so that it is then necessary to abstain from adding the mother water any longer to tile solution, and to decom- pose it by salt of soda.

The acid oughtto be pure, and particularly fi'ee from tar and sul- hurous acidl ithe tar wouhl discolour the sugar of lead, ~ind the sul-

P . . . . .

phuroos acid produce an Insoluble precipitate of sulphate of lead. .- The boilin~-v solution may be brou. glut to various densities by ,add- mg more or less water; and as tins difference produces some varmty ia regard to the crystals, the manufacturer, by a little observation, may suit the taste of his customers.

To obtain a very white sugar of lead, the metal or litharge should have no admixture of copper~ as is usual in French lead, and: Ger~ mart litharge. Its effects may, however, be obviated, by putting a tew piates of lead into the boiler. But some manufacturers do nbt wish to separate the copper, because it gives the sugar of lead a slight bluish tinge, whicffpleases the eye of many of the buyers.

It~ this solution of tl~e litharge ia the acid there remains a very sn~all residuum, which ought not to be thrown away; bu$ when a quantity of it is coi~cted, it may be treated as all ore of silver, as it is composed of tidal metal, united with oxide of copper, of lead, and some earthy substances, . -,~ ~,,

i t isa great ad;cantage in this manner of forming su ~ r of lead, by far,ins of strong pyroligneous add~ that it is not necessary to eva- porate the solutior~ for the purpose of crystallizing it, as was,:nec:e~- sary when vinegar was ttsed;?for the solution ~ deeomposedb~ being boiled, aiid part of the sugar of lead is c ~ d ;iAt6-~hith

,~tead, and of course~ pse arates in form p o t owder. [ ~ .--:~on~ MeChi 3"ore'.