od. ls46 TURNER-"INFLUENCE OB COMPOUND8 O F IRON UPON OXIDATION REACTIONS" 266

15 Fdrater and Proasprich ibid. 1837 33 2490. 20 Imprial Uhotnical Industrlea Ltd., Dy~tuRa Dlvislon, Priwakl 18 Jhaverl Tb& Vletorl; Univerrit$ dasnchester 1940. 17 Cockctd T b s d Victoria Unlveralt$ Mancheate; 1841. 18 MansBeicl C l a d , Th8 lletermination df Hydrogen $ma, London, 1828,

10 Iniperfal Chemical Induatricn Ltci., DyPstuffB Division, Private

Comnmnwalion. 21 Privak Communicalimi. 22 Itsbinowltach .I . Chena. Phys 1840 8 661.

~4 rmaiiant cmpt remi. l a b 171 3d8. 26 Hedvall, haktioiafdhiidkrait f e h r &&Ye, Lelpzig, 1838. py. 180-181.

p .NO-212. 23 Weisa Tlans.'~araday ~ o c ism 33 isai. Cmnmuniratwni.

The Influence of Compounds of Iron upon Oxidation Reactions H. A. T m m

Following the observation that certain vat dyes in the reduced form accelerate the hypochlorite oxidation of cellulose~, it haa been shown that a similar acceleration is produced by the presence of ferrous hydroxide on cotton cellulose undergoing hypochlorite oxidationa. Not only do these two kinds of accelerator agree in virtue of their ability to increase the rate of oxidation very greatly when conditions are favourable, but there is also a marked similarity in the more intimate details of the accelerated oxidation conditioned by each of them.

The establishment of this similarity appears to be an early step in showing that the acceleration of the hypo- chlorite oxidation of cellulose by active reduced vat dyes is not likely to be a highly distinctive phenomenon, but, after allowance has been made for the peculiar secondary properties of the system, is capable of direct inte retation by the same rules which govern the course o?a great variety of reactions when they are induced or accelerated by the change of an accompanying substance to a more highly oxidised stage.

The value of this evidence, provided by a study of a hypochlorite oxidation accelerated by ferrous hydroxide, is likely to be the greater, because much experimental work and theoretical speoulation have already been concerned with iron and its compounds aa oxidation catalysts. There is a useful prospect of applying some of this material a t a later stage to provide an explanation of the oxidations accelerated by Zeuco-vat dyes. In addition, the in5uence of iron and of other metab and metallic oompounds upon the hypochlorite oxidation of cellulose is of immediate technical importance, principally because of the local tendering produced by accidental deposits of these sub- stances in bleachin@. This is an occurrence which is widely known industrially, but which does not appear t o have been investigated quantitatively with the thorough- neea which its importance might Seem to warrant. As part of the investigation of the hypochlorite oxidation

of cellulose in the presence of ferrous hydroxide, mentioned above, information about the catalytic effects of iron compoun& during oxidation waa collected from a number of sources. It waa thought that the following review of this material would be of general interest and value, although it is not exhaustive, as the subject is a very large one. Some attention has also been paid to the eignificance of the material in problems concerned with bleaching and with other textile processes.

Iron Compounds aa Oxygen cawiera- h many studies upon this subjeotki'. both ferrous and ferric compounds have been shown to poasess activity, but there are well- established examples of the more intense and powerful action of ferrous compounds in reactions which are Bsalogous to oxidations accelerated by the presence of lewo-vat dyas. The action of iron compounda upon hypochlorite6 haa not been investigated very extensively4. The greater psrt of the more strictly quantitative investi- gations deals with oxidations by air1si18*14 or by hydrogen peroxide16'16*1'. Kolthoff and Sandell'* have explained the well-known disturbing effeots of the chloride ion upon the volumetric estimation of ferrous compounds by germsngsmate aa arising from the o+dation of chloride to

, mduced by the simul-

mgm Uaviara in Tsdile Prwsesee-The effect of rite of metals, their oxides, hydroxides and baeic 9 bin oaueing intense looel atback of cotton goods during

hypoohlorite blesching is we1Lknowna. I$ appeara to run parallel with the ability of moh substances to cause instability in the hypochlorite, aocelemting its decom- position with the liberation of gaeeous oxygen. Higgins'O noted the apeoial eotivity of copper oxide. K a i & n t m n S O

t : 0 n .

placed the hydroxides of cobalt, nickel, copper, tin and iron in descending order of specific activity. Kindz1, and Kind and BauraP have also made practical studies of the catalytic effects of metals, particularly copper and iron, in cotton and linen bleaching. It wm shown that the hydrogen ion concentration of the bleaching liquors wm of great importance. Cotton impregnated with copper hydroxide or iron hydroxide, and clothe with fine wires of these metals interwoven in their structure, showed. on the whole, the greatest attack by acid hypochlorite solutions. In technical experience the local deposits of iron may come from finely-divided material in oil staim, from droppings of condensed water from overhead pipes and girders, or from contact with the walls of kiers and other vesseb. The action of iron and iron compounds deposited in this way is very irregular. Their presence may sometimes appear to be without effect during hypochlorite bleaching; at other times they appear to behave as powerful accelerators. Apart from its state of subdivision and the intimacy of its association with the cellulose, the stage of oxidation of the iron in the deposit may be one of the most important factore in this action. This factor is rendered somewhat difficult to investigate because there are a number of known or reported compounds of iron with oxygen, some of them capable of existing in a number of different stages of hydration. Stumperas has shown that the deposit obtained by allowing iron to rust in water varies in com- position with the time of formation. Newly-formed rust contaim a high proportion of ferrous iron, which in one set of determinations fell from 43% to 9% FeO in 14 days.

As in hypochlorite bleaching, 60 in peroxide bleaching. Hydrogen peroxide solutions, especially when alkaline in reaction, so that both instability and oxidking activity are high, are often powerfully affected by metallic im- purities, including iron both in the dissolved condition and in the solid form. This leads to premature decomposition of the b a t h and to occesional damage of goods undergoing process8', and has rendered necessary the provision of a protective coating on the walls and circulatory system of iron kiers before they can be used for the alkaline peroxide treatment in the KauffmanhD6 and other combined scouring and bleaching processes. R ~ p p . * ~ has noted that the catalytic action of iron in the peroxide bleach is also very erratic, traces of iron compounds in the form of stain6 often causing marked damage, whilst iron wires twisted among the goods had very little effect. Suggestions have been made from time to timea7 that the catalytio activity of various substances, especially salts of man- ganese and nickel, should be employed to enhance the activity of various oxidising bleaching agents, but such a procedure is always likely to entail difficult problems in the maintenance of a controlled and uniform action upon the goods.

In epite of these suggestions, the deliberate use of iron compounda aa oxygen carriers in textile processes is rare, but there are examples of the use of other oxygen carriers. Two important ones are the use of copper and vanadium salts, aa well aa of ferrocyanides, in the production of oxidation blacks; and in the um of lead, manganese and cobalt driers when drying oils are applied to ootton and rayon. These two applications have a common feature in that they may also encourage an extension of the oxidising action to the textile material while it is being processed, or at some later stage. The accelerating action of oxalic acid in chromate dkoharges may also belong to this type of oxygen transfer, although, in several respects, the analogy is not very close. T h e action of anthra- quinone and some of its derivatives in facilitating the oxidation of sodium hydrodphite and sodim sulphoxylate-formaldehyde by such diverse agents ER vat

266 TURNER-“INFLUENCE O F COMPOUNDB O F .WON UPON OXIDATION REACTIONS” OCL 1946

dyes and air is of great im ortance in printing, and would seem to be very closely refated to the mcelerating action of the reduced vat dyes. Omk? Action in Orgalvio h’eactim- Probably the

most widely known exam le of the accelerating action of ferrous salts, showing itseyf in a relatively uncomplicated form, is Fenton’s reactioni6. The addition of a small quantity of a ferrous salt to hydrogen peroxide facilitates the oxidation of tartaric acid to dihydroxymaleic acid, of polyhydric alcohols to aldoses, of hydroxy-acids t o aldehydic acids, etc. Goldschmidt and others1@ have studied the Fenton oxidation of glycollic acid, which yields oxalic acid in the presence of ferrous aalts, whilst in presence of a ferric salt, or no catalyst at all, the pro- ducts are formic acid and carbon dioxide. It is interesting to note that Goldechmidt, following Wielande, connects the specific effect of the ferrous salts with an “oxihtione- 8to88”, an idea which curiously resembles the hammer blow theory advanced to explain the simplification of the oxidation of cellulose by leuco-vat dye acceleration.

Peroxide Theorb- The separate funations of ferrous and ferric salts in the catalytic decomposition of hydrogen peroxide, and as accelerators in oxidationa by this reagent, have been studied a t great length by Manchot and his collaborators~~, and by Wielanda. Manchot waa specially concerned to show that the catalytic activity of ferrous ions with oxidising agents in general is of the same type a~ that shown when gaseous oxygen is the oxidising agent. Ferrous compounds behave, in his view, like ethylenic compounds in tending to form an addition compound with the oxygen (he calls this the primary oxide). This idea has been maintained, with some modifications, throughout a long series of investigations- “bei allen Oxidationsprozeasen entateht ein Primdvoxyyd welchea in Allgernein den C?uwal&r einea Peroxyda besitzt”. Manchot’s views may be expressed by the following general scheme-

(i) Primary oxide isolated as such, or (i i) Fe*II + free oxygen, or (iii) FerV”rv reacts further with an acceptor --f

FeIlI + oxidation product. These views were developed early in the present century,

and the original papers should be consulted for an account of their application t o the experimental results of the action of compounds of iron and chromium in many types of oxidation. In a later paper’, oxidation processes were assumed to take place in the following three stages- (1) Association of the accelerator with the oxidising agent in simple molecular pr0portiOM. (2) Decomposition of the associated molecules to give rise to an intermediate s t a g e the primary oxide. (3) Decomposition of the primary oxide to the stable oxidised form of the accelerator and transfer of the surplus oxygen to an acceptor.

Most of the evidence advanced by Manchot tends to show that the formation of the “Primiiroxyd” only takes place readily from the lower normal stage of oxidation. Thus, if iron is the carrier, it will have completed the reaction when ferrous iron has been transformed t o ferric iron, and one or two equivalents of oxygen have been transferred t o the acceptor; unless there is a second independent mechanism which can reduce the ferric back to the ferrous stage and so cause the cycle to be repeated, the oxidation will stop. Reasoning by analogy with the known formation of addition compounds between ferrous salts and nitric oxide, Manchot and Schmidt’ suggested that essociation cornpounds of the moloxide type occur between compounds of ferrous iron and oxygen, e.g.-

FeO + 0, + Fe0.0,

Many attempts have been made to determine indirectly the possible composition of such addition compoundB, the formation of which is held to be necessasy for the activation of the oxygen. This is done by measuring the proportion of oxygen (over and above that required to transform the ferrous compound to the ferric) which is passed on to the acceptor.

A detailed treatment of similar reactions in which iron is shown to play an important part has been given by Wieland and Franke*. In the oxidation of hypophos- phorous acid by hydrogen peroxide in the presence of ferrous salts, aa many 88 17 equivalents of oxygen are transferred to the acceptor for each equivalent of ferrous

Fe“ + oxidising agent -+ F e r v o r v -+

2Fe0 + 0, + FeO-O,.OFe

iron initially present. A small part of the total oxygen is tramferred to the acceptor a t the beginning of the reaction; thereafter the transfer is slow. Wieland rejeoted the suggestion that the first part of the reaction occurs through the formation of a primary association compound of iron with a small integral number of atoms of oxygen in the molecule, thereby representing an abnormally high stage of oxidation. According to Manchot’s view, the formation of such a substance would correspond to the first rapid transfer of a small part of the total oxygen, and the prolonged transfer of the rest would be explained aa a gradual direct reduction of the ferric iron to ferrous, so rendering it capable of forming more of the active primary oxide. Wieland waa of the opinion that complex formation takes place between ferrous iron and the hypophosphite, and that the function of the ferrous iron is to activate hydrogen and to render it more easily removable by the oxidising agent. It is very likely that this suggestion is coloured by the general views of Wieland, who preferred, whenever possible, to regard the removal of hydrogen from a system undergoing oxidation as the essential feature of the mechanism.

There is some experimental evidence in favour of the idea of the formation of association compounds between ferrous iron and the oxidising agent (giving the primary oxide of Manchot), as well aa of the formation of com-

lexes between iron and an acceptor. Goard and Rideel*’**” K ave investigated the possibility of the formation of stages of oxidation higher than the trivalent in iron by a study of the potentials set up when iron salts are treated with hydrogen peroxide. They first investigated the inter- mediate formation, first suggested by Jobso, of a fugitive hexavalent cerium compound during the oxidation of sodium arsenite by air in the preeence of cerous salts. They found that a high oxidation potential, exceeding that of tetravalent cerium, waa temporarily set up before falling to that of the resultant mixture of ceric d t and arsenatess. In working with systems containing ferrous ironas, they noted a sudden increaae in the positive potential of a hydrogen peroxide solution when the ferrous salt is added, followed by a slow decay to near the original value. The lower the temperature, the slower is the fall. By titrating the hydrogen peroxide with the ferrous salt, there is some evidence of the consumption of 1.6 moles of hydrogen peroxide per mole of ferrous salt in the complete formation of the unstable compound of high oxidation potential.

Aasociation between Ozygen Cawier and, Acceptor- In oxidations carried out with hydrogen peroxide or with gaseous oxygen in presence of ferroua compounds, there is often, depending largely on the chemical constitution of the acceptor, evidence of a high and specific activity in alkaline solutions18i81. This has led to speculations upon the possibility that salts of ferric acid may be formed and may act aa very powerful oxidising agents which are much more active than the ferric oxide from which they may be aasumed to originate. A further extension of the idea is that the ferrates may form complexes with the acceptor which could still further aesist the transfer of oxygen. The occurrence of ferratea aa intermediate steps during oxidations by hypochlorites in presence of iron compounds is a possibility which may require serious consideration, because the usual method for the preparation of ferrates if4 based upon the oxidation of alkaline suspensions of ferric hydroxide with chlorine. Bohnson and Robertson** claim to have demonstrated the formation of these com- pound~ ectrographically when oxidations in the r e e n o e o?iron are taking place under alkaline conditions.

avidsonl* has shown that the absorption of gaseous oxygen by cellulose is accelerated by the presence of iron, and that thie absorption is encowaged by the presence of alkali. The Buggeetion that complex iron salts are formed has been mentioned by Davidson’*. It should be noted that the uncatalyeed oxidation of cellulose is also encouraged by alkaline conditions. Salley’d has shown that mannitol is oxidieed most readily by gaseous oxygen when ferric salts and alkali are simultaneously present, and suggested that the formation of a complex ferri- m d t e (Traube and Kuhbieraa) is an essential part of the process. In this particular reaction, iron present h i t i a l l s h the ferrous form does not contribute to the acceleration of the rewtion.

This corresponds to a poroxide FqO,,.

Oet. 1046 l"RR-"INFLUENCE 03' COMPOUNDS OF IRON UPON OXIDATION REACTIONS" 267

A &ble review of the oxygen-transfer activity of iron compounds in biological systems, with an extensive bibliography, has been given by Sterna'.

Relative Catalytic E@cienciea of Fewow and Ferric Compounds- From the results of a number of workers in thia field, a clear distinction seems to emerge between the catalysis of oxidations by ferrous and by ferric iron, respectively. The reaction when ferrous iron is present ha6 8 high initial rate which falls more or less rapidly to B low steady value. When ferric iron is present alone, the acceleration is leea intense, and the reaction prooeeds a t the enhanoed rate for aa long as oxidising agent and an acceptor are available. There ie some indication t b t oomplex formation between the iron and the acceptor and the formation of complex ions in alkaline conditions is rdricted to systems where ferric iron is the effective oatalyat. Independent observations by different workers show that the oxidation by air of ferrous iron to ferric takes plaoe more slowly in alkaline conditions, although them conditions may favour the oxidation of an acceptor. Kmus and othersa* have studied the conditions in which ferric hydroxide can act as a carrier during the oxidation of many of the sim ler carboxylic and hydroxy-carboxylic acids. The amorpiow or so-called orthoferric hydroxide is said to be by far the most energetic in this respect. I t is suggested that this activity is due in part to the ability to absorb the acids on the surface of the gel structure, and F l y to the fact that the hydrogen a tom in the hydroxyl groups a m loosely combined. They can, for instance, be replaced readily by atoms of silver. It is supposed that they ere removed by hydrogen peroxide, leaving a ferric peroxide which can act aa a powerful oxidiaing agent-

ke-OH

Be--b I I

Ohain R & h Theories- Suggestions for oxidation meohanisma which require the momentary formation of unstable intermediate products are comparatively easy t o devise, but are often difficult to test experimentally. Unlees the unusual behaviour of the eystem demands it, it is therefore better to avoid elaborate and highly specific mechisme. and to see how far the action of ferrous compounds can be explained by the general theories of chain reactions. Such theories can be summtuiaed in the

The reaction takes place in three esaential stages- (a) the ferrous compound is changed to ferric by the oxidising agent, and the energy liberated by this reaction activates the acceptor, increesing the reactivity of this substanoe and initiating the chain; (b) the activated acceptor reacte with the oxidising agent, liberating a further amount of energy which can activate a further amount of the acceptor; (c) this in turn reacts with a further quantity of oxidieing agent and the cycle of aotiva- tion followed by oxidation continues while there are remtants present, or until the energy available from the oxidation ie diverted to Bome other reaction. When this diversion occurs, the chain ie said to be broken, and the rate of the main oxidation falls to its unaccelerated value. The effect of the initiating molecule of ferrous salt is then completed. The length of the chain, i.e. the number of times that the main reaction repeats itself after initiation, is shown by the total number of equivalents of oxygen transferred to the acceptor for each equivalent of ferrous iron present a t the beginning. On the bagis of this simple form of the theory, and neglecting possible intermediate detaila of the main oxidation, the acceleration of the oxidation of cellulose by ferrous compounds, and the acceleration by reduced vat dyes, may both be explained in the same way, regarding the change from reduced to oxidised form of the aooelerating substance as the initiating reaction. hco-Com ounde ma have an advantage over ferrous iron in d t a h t y for t&s function, because their known etrong association With the oellulose q a y assist the transfer of the initial wtivating energy.

In previous work on oxidation by chain reaction# where iron functions aa the initiator, much attention haa been paid to oxidstione dected by hydrogen peroxide, for this

following way.

oompound has provided a convenient source for highly reactive radicals, particularly the hydroxyl radical. The formation of this radical has been regarded as the activa- tion, the reduotion of this radical by the acceptor, with re-formation of the hydroxyl ion, providing the energy necessary for continua,tion of the chain. The postulated formation of hydroxyl ions during the reaction has, in eome m e w e , provided an explanation of the observed influence of hydrogen ion concentration on the rate of oxidation.

One of the simplest examples of the application of these ideaa, and one which may be specially suitable in the con- sideration of oxidations of cellulose, is given by Taylor and Gouldaa for the air oxidation of alcohols photocatalyaed by hydrogen peroxide. The initiation of the chain is aocomplished by the formation of hydroxyl radicals from the hydrogen peroxide through the action of light-

The chain reactions are then- (1) q O , f h v + P OH

-- (2) R C ~ O H + 6~ -+ R ~ H O H (radical) + H,O (3) RCqOH + RPHOH + 0, --f BRCHO -+ /OH +H,O In order to explain the catalytic decomposition of

hydrogen peroxide by ferrous compounds, Haber and Willst&ttera7, m d Haber and WeissaB, required the presence of radicals derived from two of the possible ions that can come from hydrogen peroxide, viz. OH- and Oa-.

The chain i s initiated- (1) Fe++ + %O, -+ Fe+++ + OH-, + OH

It is then carried on by the reactions-

(2) O h + ~ O , + ~ O + H O , I (3) HO, + q0, + 0, + -0 + @

--I

---- ---_-- -----

If the chein-propagating radical and the initiating ferroua ion react, they put each other out of action and the chain stope--

(4) Fe++ + OH + F e w + OH- Externion of this idea to the peroxide oxidation of

cellulose oatalysed by Fe* may be in two directions. The cellulose might function m the chain-breaker in the above series of reactions-

In this case, the efficiency of the reaction would be low, the amount of cellulose transformed for a given conaump- tion of ferrous iron and oxygen being small unless the oxidation of the cellulose set up a chain in a different direction. It would be more profitable, and corresponding more with such experimental facts as are available, to regard the cellulose as the acceptor in a reaction similar to that suggested by Taylor and Couldsa (see above), e.g.-

(1) Fe++ + KO, -+ Fe+* -t OH + OH-

(4a) Cellulose + OH += Oxidised cellulose + OH-

/C!HOH

* Denotes radlcal

The application of the concent of chain reaotion mechanisms has been less common where hypochlorites have been the oxidising agents. Kauffmann~e has suggested the following series of reactions where Orange I1 (CoEour I d e x , No. 161) is oxidised in the joint presence of sodium hypochlorite and hydrogen peroxide. The rate of destruction of the dye when both of these substances are present is much greater them in the presence of either of them alone. In this scheme, hydrogen eroxide is regarded rn the initiator, and hypochlorite ea t f e principal oxidising agent. It will be seen that, in addition to invoking the formation of free radicals derived from the peroxide and the dye molecule, Kauffmann also suggested the preliminmy formation of an Bssociation compound between the initiator and the hypochlorite ion.

268 NABAR C TURNER-“OXIDATION OF CELLULOSE BY SODIUM HYPOCHLOlClTE” Oct. 1946

(1) Z?&itkZtiOn-

( 2 ) C‘hain reactiom- &O,+ ClO-+&O,GlO-+Cl~ +HO,* +HO*

R& (Orange 11) + OH* e H,O + RH* RH’ + C 1 0 - + R (oxidised Orange 11) $. Cl-

Denotes that the substanre exists as a fiec- radical The application of ideas such as these to explain the

action of a reduced vat dye or of a deposit of ferrous hydroxide in accelerating the oxidation of cellulose meet8 with a number of difficulties when an attempt is made to substantiate them experimentally. (a) The system is a heterogeneous one, so i t is difficult to obtain a quantitative value for the effective concentration of either accelerator or acceptor undergoing oxidation. (6) Although i t may bo possible to measure the consumption of the oxidisihg agent, there is as yet no absolute method of assessing the amount of oxidation product formed. ( c ) The rate of reaction in the solid substrate (acceptor) may be in- fluenced by the differing accessibility of different regions in the fibre to the surrounding solution or atmosphere.

When the attempt is extended to deal with light- tendering phenomena in presence of air or an oxidising a,gent, the complication increases, for the action of the light can be directed to influence the oxidation in various ways. It can produce the initiator, e.g. by photo- reduction from a chemically less active form, and i t can be imagined to discharge ions. forming very reactive free radicals a t various stages, either continuing the sequence of chain reactions, or providing a means of breaking this sequence.

It should be emphasised that full investigation of mechanisms requiring tho existence of very reactive entities such as free radicals can only be made when fully quantitative rneasuroments are possible, since the presence of these radicals can only be inferred indirectly. They have normally such very short life that i t ifl not possible to isolate them a t any stage. DEPARTMENT OF TEXTILE CHEMISTRY

COLLEGE O F TECRNOLOaY MANCHE~TER

(Received on 17th Pebmary, 1945)

REFEEENCIOB 1 Nabar Eicholetleld arid Turucr this Jour., 1937, 53, 6. 2 Nubur) arid Turner ibid. 1945 61 258 5 Kind Uas Bleicheri der iyun;enj&em’ Berlln, 1932, pp. 139-141;. 4 Manc’hot arid Wilhehus, Ber., 1901, 34: 2479. 5Manchot Bnnalen 1902 325 93. G Maiichot’ibid 1962 324 106 7 Manchot’and‘bchrnh lfh lQS2 65, 98. 8 W’idand and Frauke,’An&len, lea7 457 1. 9 Rirchc, Die l f e d e u t ~ ? ~ der organlsclin Pirozvde .fur die Chendeclre

Wiaaeiaeclaajt und Technik (Aiirrns Vortrtlgc, New Hcrlra, No. 34). Stuttgart, 1056, pp. 17-18.

10 Baudiachc, Ber., 1021, 54, 407. 11 Raudiacha and Base, ibld., 1922, 55, 2696. 12 Palet and-Dhar, J . Phvs. Cheffk., 1926, 29, 799; 192Li. 30, 939; 1928,

13 Dnvfdson, J . Textile Znet., 1032, 23, T95. 14 Balky, J . Phge. Cham., 1934, 38, 449. 16Benton Uhm. Ncwn, 1876,23, 190; 1881, 43, 110; J.C.S., 1694, 65,

16 Goldschmiddd d., Be?., 1026, 61, 223; Annalvn. 1933, 502, 1. 17 Nerz and Wagner, Ber., 1937, 70, 446. 16 Kolthofl and Sandell, Textbook of &ua?itilalive Inorganic Analy8io

New York, 1936, pp. 476-477. For a general discussloll or; induced reactions In analytical work 8ce Kolthoff and Livingston, Ind. En& Chem.; Anal. Ed., 1936, 7, 209.

DOKauffmanu Melliand Teztilber., 1928, 9, 675; 1931, 12, 624. Sue ulao i,arrn and Nagorsky, Zelleloff 14. Papier, 1937, 17, 58.

21 Kind, Melliand, 1930 1, 1627. 22 Kind and Baur Melliund Textilber. 1931, 12, 1n4. 21 Eitumper, Bull. hot. chim. Relge, 1926, 34 150. e4 Kind, Due Bleiehen der Pllmrenlwwn, derlh, 1932, up. 1C1-16.&. 26 Kauffmann, Melliund Teztzlber., 1930, 11, 372. ZERupp Dger 1936 74 685. 21T~ytid Recdrdw, i92d, 46, No. 544, 03; Wmal, Chem. Abe., 1927,

28 Qomd and Rideal, Proe. Roy. Soe. d, 1924, 105, 135. 28 Gourd and Rideal, iDU., 1924, 105, 148. 30 Job, Ann. Chim. Phus., 1900, (vil), 20, 205; Cmbpt. rend., 1902, 134,

31 Wilson, J.S.C.I. , 1920, 39, 177T. 32 Bohnson and Robertson, J . Amer. Cliem. Soc., 1923, 45, 2495. 33 Trauba and Euhbier, Ber., 1932, 65. 187. 34 Stern, S rn~oeium mi Res9iratorv Enzunrra, M’~KI, (IIIEIII , 1942, 1 ~ 1 , .

36 Kriui!e-<t nl. , i M . , 1935, 68, 1734; 1030, 69, 805; 1937, 70, 439,

32 1281.

- 699; ’19u0 77, 20.

IsH~ggiIinE, J.S.C.I., 1911, 30, 1926.

21 996.

1052.

74-103:

443 1716. 36 Taylo; and Oould J . PhU6. C‘hem. 1933 37,367. 37 Haber‘and Willstitter I3rr. 1931 ‘64 !&a4 38 Haber and Wdss Pr;. Roi . Soc ’d,’1934 147 332. 3 9 Kauffmann Rer.,’l932, 65, 179. Ser also‘ B H & ~ , D I P dkltoieruny

drr Blcwhlauge, Dbsertatlon, Btuttgart, 1933

The Oxidation of Cellulose by Sodium Hypochlorite in Presence of Ferrous Hydroxide

G. M. NABAR and H. A. TURNER Imtroduction- The rate of oxidation of cotton cellulom

by dilute solutions of hypochlorite has been shown to be much increased if certain vat dyes are also present in the reduced form upon the fibre. This acceleration of the oxidation has been studied in det’ail by Nabar, Scholefieltl find Turner’, who arrived at, the following conclusions.

( 1 ) The accelerating action takes place in the complete tibsence of light.

( 2 ) Those vat dyes which exhibik greatest activity in promoting the tendering of the cellulose on which they are dyed, if the tendering is brought about by the joint action of light and air or of light and hypochlorite, are also, in general, when prosent in the reduced form, the most active in accelerating hypochlorite oxidation in the dark.

(3) The accelerated hypochlorite oxidation of cellulose appears to be simpler and to retain the same reaction mechanism more consistently over wide variations of hydrogen ion concentration than does the slower un- accelerated oxidation. For instance, in the accelerated oxidation, when hypochlorite solutions of different pH are used, the following relations are wholly or substantially independent of pH.

( a ) The reducing value of the oxidised cellulose, as meaniired by the copper numbcr, is directly proportional to the oxygen comiuned.

( b ) There is a straight line relation between the oxygen consumption and a value which has been named the “corrected oxidation potential” of the hypochlorite solutions employed. If the corrected potential is repre- sented by El, EH being the potential, referred to the normal hydrogen electrode, of a bright platinum wire immersed

in a hypochlorite solution, the pH value of which is h, then-

El = E H + 04Y18 h. It has been suggested that El may bo considered as the difference between a value representing the oxidation potential of the hypochlorite and a value representhg the oxidation-reduction potential of the cellulose.

( c ) The cuprttmmoilium fluidties of the cellulose which has undergone accelerated hypochlorite oxidation a t different p H values, when plotted agalnst the cnrrespond- ing oxygen consumptions, lie on a smooth curve.

The simple relationships described in (a), ( b ) and ( c ) do not hold for the normal slow hypochlorite oxidation of cellulose.

This behaviour of the hypochlorite-leuco-dye-cellu- lose system, whilst resembling qualitatively many other reactions in general and biological chemistry, has several features of peculiar interest, and i t has already shown promise of assisting in the interpretation of some of the complex problem of fading and tendering. The study of this type of accelerated oxidation should therefore be capable of extension in several directions, viz. by the me of (i) accelerators other than vat dyes, (ii) oxidising agents other than hypochlorites, and (iii) substrates other than cellulose.

In the present paper an aocound is given of experiments in which the accelerating system-

leuco-vat dye + vat dye has been replaced by the system-

ferrous hydroxide -+ ferric hydroxide It is s h o w that the hypochlorite oxidation of cellulose,