Chromatographic Investigations of Smokeless Powder DERIVATIVES OF DIPHENYLAMINE FORMED IN DOUBLE-BASE POWDERS DURING ACCELERATED AGING W.A. SCHROEDER, EARL W. MALMBERG', LAURA L. FONG, KENNETH K. TRUEBLOOD, JANET D. LANDERL, . ~ N DEARL HOERGER2 Caluornin Z n s t i t i ~ t eof Technology, Pasadena 4, Calg.
B y means of the chromatographic method a study has been made of the products which are formed from the stabilizer, diphenylamine, during the accelerated aging of a bommercial, American, double-base powder. I t has been established that in the conrse of the aging the diphenylamine is converted successively into a large number of nitro and nitroso derivatives which include as simple a compound as N-nitrosodiphenylamine and as highly nitrated a compound as hexanitrodiphenylamine. Procedures have been devised for the roughly quantitative determination of these derivatives in samples of smokeless powder, and it has been found that one half to two thirds of the original quantity of diphenylamine is converted into these nitro and nitroso derivatives, and that the remainder produces compounds of unknown nature. Seieral schemes are proposed to explain the successive conversion of one derivative into another, but it has not been possible to decide which, if any, is correct. The chromatographic methods are described.
tiori of the st,ate of the stabilizer in any given sample of povvcior will give information about t,he history of this powder and perhaps an indication of its future usefulness. The present article describes the result's of a qualitative and quantitative determination of the many compounds which are formed from diphenylamine in the course of the aging of double-base smokeless powder, and some of the conclusions which may he drawn from these results are discussed. This investigation, which involved t'he analysis of difficult.ly separable mixtures of derivatives of diphenylamine from one another and from other constituents of doublebase powder, was made possihle through the application of the chromatographic technique. The quantitative estimation of each isolated derivative was made spectrophotometrically. The present study was made on samples of a typical commcrcial lot, of American Ballistite, designated as JP 204, the composition of which is given later. Small samples of the powder were heated a t 71" (2. in separate vented tin containers for various periods up t o 258 days.
IPHEXYLARIINE has long been used as a stabilizer for smokeless powder. I n this capacit,y it presumably stabilizes the powder by combining continuously with the nitrogen acids and oxides which arise from the decomposition of the nitrocellulose and thus decreases the autocat,algtic effect of these products on the further decomposition of the uitroccllulose. From the work of Davis and Ashdown ( 6 ) , Hcclrer and Hunold (a), and ot,hers,it is generally assumed that, in the course of the stabilization, the diphenylaniinc undergoes a series of nitrosations and nitrations which eventually yield a highlv nitrated product. Thus, diphenylamine presumably is first nitrosatcd t o form N-nitrosodiphenylamine (the Fischer-Hepp reaction). This compound is then oxidized to 4-nitrodiphenylamine which, in turn, is nitrosated; the N-nitroso-4-nitrodiphenylamine subsequently rearranges and is oxidized t o form dinit,ro derivatives. Similar reactions yield trinitro derivatives, the apparent end products. The formation of some of these derivatives is evident from the results of Davis and Ashdown (6) who isolated 2,4'and 4,4'-dinitrodiphenylamine and 2,4,4'-trinitrodiphenylamine from single-base powder in a n advanced state of decomposit,ion. Becker and Hunold ( 2 ) followed the react,ions in heated powder by means of color tests. Hoviever, except for the evidence provided by the several derivatives of diphenylamine which were isolated by Davis and Ashdown, support for the actual presence of the postulated compounds and for the mechanism of thrir formation is based on relatively meager data. As Davis and Ashdown mentioned, if the course of the reactions of diphenylamine in powder is known, then the det,rrmina-
When t,he originally pale green grains of JP 204 were heated a t 71 C., they became increasingly blue-green during the period of thc depletion of the diphenylamine, and after this period the blue-green was gradually replaced by a brownish coloration which increased in intensity. Samples which had been heated for 174 and 258 days appeared to be red-brown, but an axial section showed a red central portion which was surrounded by a brownish yellow part and, in t,he 258-day sample, an additional outer layer of red. These two samples were actively evolving red fumes of nitrogen dioxide. Wit,hin a few hours after heating was begun, a condensate became evident on bhe sides of the containing vessels and increased somewhat in amount with continued heating. Investigation of this condensate from a sample which had been heated for about, a month showed that it consisted largely of nitroglycerin, and that small amounts of dinitro and trinit,ro derivatives of diphenylamine were also present,. The heating produced a loss in weight which amounted to about 1% a t the end of the first month arid to about 2% a t the end of 3 months. To separate the soluble constituents ol the powder (nitroglycerin, derivatives of diphenylamine, etc.) from the insoluble nitrocellulose, each sample was first extracted with methylene chloride. These extracts were greenish yellow to yellow-brown in color. The color of the nitrocellulose residues of the bluegreen samples was somewhat' bluer but the color of the residues of the other samples was little changed. The blue color could I)c extracted with methanol. The significance of all of these changes and their relation to thc chemical reactions taking place in the powder will be discussid i n a later section.
1 2
Present address, Ohio State University, Columbus, Ohio. Present address, University of California, Berkeley, Calif.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
becember 1949
1.2
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30 40 50 60 40 TIME OF HEATING AT 7I0C.,DAYS
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90 TIME OF HEATING AT 7I0C., DAY5
Figure 1. Formation of Derivatives of Diphenylamine in Ballistite JP 204 during Heating at 71" C. for Time Period Shown within Dotted Lines of Figure 2
Figure 2. Formation of Derivatives of Diphenylamine i n Ballistite JP 204 during Heating a t 71' C.
QUALITATIVE AND QUANTITATIVE ANALYSES
are quantitabivelv unimportant in sheet powder when compared with the others. It is probable t h a t one of the dark pigments (the blue one) which is difficult to extract from the nitrocellulose is related t o diphenylamine blue (N,N',N"-triphenyl pararosaniline hydrochloride). Each sample of powder contained one or two unknown compounds which could be isolated during the chromatographic separations, but the quantities were insufficient for identification. These compounds were strongly adsorbed; their source probably was the brown material which remains on the nitrocellulose after extraction with methylene chloride but which is soluble to a very slight extent in this solvent. I A study of the highly colored pigments in samples which were not depleted of diphenylamine indicated t h a t three substances (blue, green, and purple) were present, and t h a t the blue substance reached maximum quantity after one day, the green after 3 days, and the purple after 4 days. The materials seem t o form and decompose rather rapidly. The green pigment was the predominant one, whereas the purple compound was never present in appreciable amount. It was estimated that at no time did the sum of these compounds account for more than approximately 5% of the original diphenylamine.
By methods described later, roughly quantitative determinations ( * 5 % ) of the predominant nitro and nitroso derivatives of diphenylamine were carried out on a series of eleven samples which had been heated for various times. Table I gives the quantity of each derivative in milligrams of the compound per gram of powder; Figures 1and 2 show the increase and decrease of each compound plotted in terms of the quantity of diphenylamine to which each derivative is equivalent. To simplify the presentation, the portions of the curves of the trinitro and tetranitro compounds which lie within the region of Figure 1 were omitted from this figure. Table I also shows the quantity of diphenylamine to which the sum of the compounds is equivalentthat is, the amount of the original content of diphenylamine which is accounted for by these derivatives. I n addition to the compounds listed in Table I, 2,4-dinitrodiphenylamine and N-nitroso-2-nitrodiphenylamine have been detected in heated powder. Good though indirect evidence indicates that N-nitroso-4,4'-dinitrodiphenylamineand possibly N-nitroso-2,4'-dinitrodiphenylamine may be formed. Preliminary experiments in which the Ballistite was heated in the form of sheet rather than extruded cvlindrical grains showed that 2,4-dinitrodiphenylamine and N - nitroso - 2 - nitrodiphenylTABLE I. DERIVATIVES OF DIPHENYLAMINE ISOLATED FROM CRAMS OF BALLISTITE JP amine were present in de204 AFTER STORAGE AT 71 ' C. tectable though very small Days of heating 0 2 4 8 20 35 48 82 124 174 258 quantities, but neither comYellowa Red Yellowa Rad Content, mg./gramb pound was found in the Diphenylamine0 7 . 1 1 4.27 1 . 6 0 0.0 .. .. .. N-NO-DPAd 0.42 2.08 3.55 4 . 4 7 2:36 o:is o:is o:oi powder heated in the form ... . .. ... .. .. 2-NOi-DPA 0 . 0 8 0.13 0.10 0 . 3 1 0 . 2 4 0.09 . . . . . .. of grains. Since the latter 4-NOS-DPA 0.02 0.07 0.09 0.14 0 . 3 5 0.18 0164 : : , . . . . . .. N-NO-4-NOicompound is labile, failure DPA . . . . . . 0.45 0 . 9 6 0 . 2 1 . . . . .. .. .. .. 2,2'-Di N Oit o detect i t in the grains DPA . . . . . . 0.04 0.29 0.45 0 . 4 2 0.04 . . . . . . . . .... may well be attributed t o 2,4'-D1NOi-DPA . . . . .. 0 . 1 9 1.01 1 . 5 1 0.95 . , .. .. .. .. 4,4'-DiNOi-DPA . . . . . . 0 . 0 6 0.56 0.83 0 . 4 7 .. .. .. . . .. .. its decomposition during the 2,2' 4-TriNOzdPA . . . . . . 0.02 0.16 0.67 1.36 2 . 0 8 1.84 0.06 , . period between removal of .. .. 2.4 4'-TriNOithe samples from the ovens DPA . . . . 0.01 0.34 1 . 5 7 3 . 2 1 2 . 1 8 0.01 Tetra NOz-DPA . . . . . . . . 0 . 0 7 0.23 3 . 5 1 7.52 2:75 0:57 0131 0:45 and the execution of the PentaNOi-DPA . . . . . . . . 0.09 2 40 0.75 0 . 9 1 0.80 HexaNOz-DPA . . . . . . . . .. 4 75 6.25 6 13 5.96 analysis; the absence of the Picrio acid . . . . . . . . . . 0 16 0 . 0 0 . 1 8 0.26 former compound may be DPA eauivalent to sum of compounds associated with the differWeight 7 . 5 5 6 . 2 4 4.79 4 . 6 8 4.65 4 12 4.03 4.10 4.70 4.37 3.04 3.05 3.01 Per cent 100 83 64 62 62 55 63 54 62 58 40 40 40 ence in physical form of T h e quantities i n the yellow,portions are plotted in Figure 2. the powder. No attempt was Results are expressed in milligrams of each compound isolated from one gram of powder; where n o value is given the quantity is less than 0.01 mg. made t o find the N-nitrosoc The decrease of diphenylamine is not plotted i n Fjgures 1 and 2. dinitro derivatives in the d A sample which had been heated for 5 days contalned 5.33 mg. of N-NO-DPA per gram of powder. grains since these derivatives I
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INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
The analytical results just given provide a factual basis for a discussion of the sequence of reactions involving the derivatives of diphenylamine in smokeless powder during aging at elevated temperatures. In general the picture is not greatly different From that postulated by earlier workers in the field. Specifically, the anticipated C-nitro and N-nitroso derivatives of diphenylamine have been found in smokeless powder a t various stages of aging, but evidence for the presence of C-nitroso derivatives of the type of 4-nitrosodiphenylamine is lacking. Figures 1 and 2 suggest that the derivatives which were isolated are formed in a complex series of consecutive and competing reactions, but Table I shows that these are by no means the only reactions which derivatives of diphenylamine undergo since the isolated derivatives do not account for more than 55 to 6570 of the original diphenylamine
Vol. 41, No. 12
diphenylamine have combined with a carbon atom from some source, presumably nitroglycerin or nitrocellulose, to give the triphenylmethane dye. Such a reaction would be expected to occur in steps so that the presence of intermediate compounds, which contain one or two diphcnylamine rests attached to a carbon atom, is to be anticipated. Athough there is no evidence for the formation of such compounds, it is not unreasonable t o assume that some reaction occurs between the diphenylamine and the nitroglycerin and/or nitrocellulose t o produce t h e hrown color of the agpd powder,
FATE OF DPPHEhY LAIMINE UNACCOUNTED FOR
Figure 3 shows the percentage of the original diphenylamnr accounted for as a function of the time of heating of the powder The recovery of diphenylamine in the form of its derivative6 decreases rapidly during the depletion of diphenylamine and is then relatively constant throughout the remainder of the heating period. Whether the decrease and subsequent increase in recovery between 20 and 120 days are real or merely result from error in analysis cannot be answered n i t h certainty although the regularity of the change would seem t o reduce the probability that error is wholly responsible. Two obvious possibilities of loss immediately suggest themselves -loss by volatilization during heating and incomplete extraction before chromatographic separations. That loss of diphenylamine or its reaction products is unimportant was shown by the following experiment: A 37gram sample of powder was heated for 4 days a t 71 C. in a slow stream (10 ml. per minute) of dried air, which was then passed through two traps a t dry ice temperature. The powder lost 217 mg., and a total of 215 nig. was condensed between the heating unit and the traps or in the traps-that is, effectively 100% of the volatile material was condensed. Although the heated sample contained originally 270 mg. of diphenylamine, only 1.1 mg. of diphenylamine in the form of its derivatives were present in the condensate; since diphenylamine alone of the compounds under consideration is appreciably volatile, it probably first volatilized and then reacted in the condensate. The remainder of thr condensate consisted of water and nitroglycerin and perhaps some diethyl phthalate. T h a t the ponder behaved normally under these conditions is shown by the fact that about 80% of the original diphenylamine had reacted and 68% of the original amount could be accounted for (compare with Table I). I n an effort to determine whether the nitro and nitroso derivatives of diphenylamine were incompletely extracted, the method of Cook (6)for “total diphenylamine” was applied to the nitrocellulose residue after extraction. About 1% of the original diphenylamine was found in thls residue, and i t ~3-mconcluded that extraction was essentially complete. Application of the procedure to unextracted powders gave results in which the diphenylamine accounted for was in good agreement with thai determined by chromatographic methods. It was concluded chat the procedure for ‘“total diphenylamine,” if carried out caretully, gives a good indication of the amount of diphenylamine itself or diphenylamine and its simple derivatives which are present in the powder; however, when this procedure is applied to a powder which has been depleted of diphenylamine, it does not, any more than does the chromatographic piocedure, give a satisfactory estimate of the original quantity of diphenylamine. Although only a relatively small amount of diphenylamine was present in the form of the blue, green, and purple pigments, the formation of these compounds indicates a possible reaction path for diphenylamine. Because the blue compound contains the cation of diphenylamine blue, it is evident that three molecules of
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40 80 120 160 200 240 TIME OF HEATING AT 71’C,DA%
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Figure 3. Percentage of Original Diphenylamine Accounted for as a Function of Timc of Heating
Figure 3 shows that the greatest loss of diphenylamine occurs during the period of depletion of diphenylamine itself, and it might be concluded that all of the loss occurs by some reaction of diphenylamine. However, experiments have shown that the less highly nitrosated and nitrated derivatives may also account for some of the loss. For example, specially prepared powders which originally contained derivativcs of diphenylamine as “stabilizers” instead of diphenylamine itaelf were heated until the derivative was depleted; it was found that, if M-nitrosodiphenylamine or 2-nitrodiphenplamine were the compound originally present, only about 60% could be recovered in the form of other derivatives. However, if i t were N-nitroso-4-nitro diphenylamine or 4,4’-dinitrodiphenylarnine, recovery was essentially quantitative. If the increase in recovery of diphenylamine in JP 204 between 50 and 120 days (Figure 3) is real, then some unknown compounds which are capable of reconversion to simple nitro derivatives must have heen formed during the prrd i n g period SUGGESTED REACTION SYSTEMS
T o explain t,he occurrence of the derivatives of diphenylamine found in powder and their progressive alteration during storage, certain reaction systems may be proposed. The agent or agents by which diphenylamine is converted into its derivatives in smokeless powder are uncertain although there is considerable speculation in the literature. I t may be that the organic nitrates in the powder, nitroglycerin and nitrocellulose, themselves react directly with the diphenylamine and its derivatives. On the other hand, the nitrates may decompose into such nitrating agents a4 nitrous acid, nitric acid, nitrogen dioxide, etc., which may react independently or perhaps may be in a n essential equilibrium with each other so tjhat there is effectively a. single “nitrating agent’’ which is responsible for the reactions. Regardless, however, of the actual agent by which the conversion of the stabilizer is effectcd, the results of these studies suggest a number of schemes by means of which one derivative may be converted into another. Various types of reactions which may reasonably be expected to occur will be considered firiit
INDUSTRIAL AND ENGINEERING CHEMISTRY
December 1949
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Scheme 2 (Figure 5) is based upon a series of nitrosations, denitrosations, and nitrations, but does not involve rearrangements or the formation of C-nitroso compounds. I n scheme 2 the only nitrosation considered is the original nitrosation of diphenylamine itself. It is presumed that this is the main reaction of diphenylamine (other than those reactions which result in unrecovered compounds), but that some direct nitration t o the mononitro derivatives also occurs. Supposedly, then, N-nitrosodiphenylamine is nitrated largely t o N-nitroso-4-nitrodiphenylamine, which is further nitrated although some denitrosation results at this stage. Since the accumulation of nitro groups produces increasing instability of the N-nitroso bond, it is predicted t h a t , after the formation of the N-nitrosodinitrodiphenylamines, essentially complete denitrosation occurs and that further reaction is by direct nitration. The major paths of reaction which this scheme proposes are shown by heavier arrows. Schemes which are more or less hybrids of schemes 1 and 2 may also be devised; a portion of such a hybrid is scheme 3 (Figure 6).
and then various schemes t o explain the entire series of conversions will be proposed. With considerable assurance i t may be said ( a ) that direct N-nitrosation occurs since no other process would be expected t o yield N-nitrosodiphenylamine and i t is also probable ( b ) that denitrosation occurs. Direct nitrations of the phenyl rings t o be considered are (c) direct nitration of amines (includes partially nitrated derivatives) and ( d ) direct nitration of nitrosamines (which may be accompanied or followed by denitroaation). The classical explanation ( 2 , 6) of the conversion of diphenylamine into its derivatives is (e) the rearrangement of Nnitrosamines to the C-nitroso compound (the Fischer-Hepp reaction) and subsequent oxidation. Another possible type of reaction is (f) the oxidation of a n N-nitrosamine t o the N-nitramine with subsequent rearrangement, although there is no evidence for reactions of this nature. It seems unlikely that (g) multiple simultaneous nitration, ( h ) denitration, or ( i )rearrangement of a nitro group from one carbon atom to another would occur t o any extent. There is no evidence t h a t reaction in the phenyl rings of diphenylamine occurs in positions other than those ortho and para t o the amino group. On the basis of these types of reactions, several schemes to explain the entire series of conversions may be proposed. The classical mechanism of nitrosation, rearrangement, and oxidation is shown in scheme 1 (Figure 4). Since Davis and Ashdown (6) and Becker and Hunold ( 8 ) did not find derivatives which were more highly nitrated than the trinitro stage, no scheme was advanced by them t o explain the formation of tetranitrodiphenylamine and more highly nitrated compounds. However, because the preparation of the N-nitroso derivatives in the laboratory becomes increasingly difficult as the number of nitro groups in the molecule increases, the probability t h a t the formation of tetranitrodiphenylamine from the trinitrodiphenylamines occurs by this type of reaction is decreased.
EVIDENCE FOR OR AGAINST THE PROPOSED SCHEMES
A simple kinetic treatment (21) has been made of the results for the entire period subsequent to the initial depletion of diphenylamine. I n this treatment i t is assumed that the reactions are all first order with respect to the diphenylamine derivatives and of the same (undetermined) order with respect t o a single hypothetical “nitrating agent,” whose concentration was found to increase more or less regularly with the time of heating. I t is further assumed that the system is “closed”that is, that derivatives do not form unknown compounds and are not formed from obscure sources; this assumption is, of course, not in complete accord with the data. Reaction schemes 1, 2, and 3 were given special consideration. When scheme 1 was used, no rate constants could be found which would fit the observed data satisfactorily; in particular i t was not possible t o account for the rapid rise in the concentration of N-nitroso-4-nitrodiphenylamine. Scheme 2 was not tried in detail but apparently would work out fairly well. Scheme 3 with variations was studied most completely, and i t was found that the observed increase and decrease of the compounds could be represented rather well. However, substantial agreement could still be N 4 obtained if the denitrosation of N-nitroso-4-nitrodiphenylamine were omitted from this scheme. The mathematical treatment of the results ib not able t o point positively to one scheme NO m2 or another’ as correct, but i t does indicate that scheme I is less likely than either scheme 2 or 3. The data of Figures 1 and 2 indicate that N-nitrosodiphenylamine and tetranitrodiphenylmD2 amine are relatively less reactive than their &QwE immediate precursors and postcursors, and this is substantiated by the calculated reaction-rate No2 constants. I t is probable t h a t these compoundb (y-@U2 do not react appreciably until each has accumulated to a considerable extent and until there m2 NC has been a considerable (and rapid) increase in the concentration of the “nitrating agent.” The constants, likewise, substantiate the deactivating effect of a nitro group in the 2 position. hi2 No \ Experiments with a series of powders into C O O 2 X ~ ~ ~ Nl 0 2 - (T 3 - & 3O7 O Z ~ which had been incorporated various derivatives of diphenylamine in place of diphenylamine yielded results which have some significance; each of these various powders con- 2 0 : 0 m 2 tained one of the following compounds: NFigure 4. Scheme 1 for Explaining Conversions nitrosodiphenylamine, 4-nitrosodiphenylami~e~
0-to
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 41, No. 12
amine probably involves direct iiitration to N-nitroso-4-nitrodiphenylamine rather than rearrangement and oxidation. Whatever the role of the rearrangement may be, i t probably decreases as the compounds become more highly nitrated, and probably the formation of the trinitrodiphenylamines and more highly nitrated compounds involves direct introduction of the nitro group into the molecule. RELATION BETWEEN STATE OF STABILIZER AND CONDITION OF POWDER
The present studies provide methods by which it is possible to determine roughly quantitatively the state of the diphenylamine originally incorporated as a stabilizer. However, answers have not been obtained for such questions as the following: What are the agents which bring about thcse reactions of diphenylamine and its derivatives? If nitroglycerin and nitrocellulose are not themselves directly involved, what changes do they undergo in order to produce the active compounds? What effect does the stabilizer have upon these reactions of nitroglycerin and nitrocellulose? Cntil we can ansyer these questions we do not believe that the relation between the condition of a powder and the state of the stabilizer is sufficiently understood t o permit conclusions about its ballistic usefulness or its safe life to be drawn from analytical data alone.
m2&&&2
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CHROMATOGRAPHIC METHODS
Figure 5. Scheme 2 for Explaining Conversions
’
2-nitrodiphenylamine, &nitrodiphenylamine, 4,4’-dinitrodiphenylamine, 2,4,4’-trinitrodiphenylamine,and hexanitrodiphenylamine. With the exception of the powder which contained 4-nitrosodiphenylamine, the heated powders were always found to contain the derivatives to be expected on the basis of scheme 2 (or schemes 1 and 3 if the Qnitroso derivatives are omitted). Only traces of N-nitroso-2-nitrodiphenylamine were present in t h a t powder which originally contained 2-nitrodiphenylamine; yet N-nitroso-4-nitrodiphenylaminewas an important product from 4-nitrodiphenylamine. Denitrosation was convincingly demonstrated by the isolation of 4-nitrodiphenylamine from that powder which originally contained N nitroso-4-nitrodiphenylamine. 4-Nitrosodiphenylamine was found t o be a very reactive compound which was depleted more rapidly than diphenylamine itself; small amounts of 4nitrodiphenylamine were isolated but the remaining derivatives were unknown, and the dark colored compounds which were formed did not correspond t o those which were isolated from commercial Ballistite JP 204. The reactivity of 4-nitrodiphenylamine is such that it probably would not accumulate in powder under any conditions and that i t was never detected is therefore not surprising. Failure of the 4-nitrosodiphenylamine to yield an important percentage of recognizable derivatives is perhaps not unexpected, since in this experimental powder its concentration was many fold greater than it could ever be in a normal powder; therefore the type of reaction may have been different. It may be concluded, then, that the first reaction of diphenylamine in smokeless powder, other than t h a t conversion which leads t o undetected compounds, is the nitrosation to N-nitrosodiphenylamine, a reaction which has long been postulated. As is indicated by Figures 1 and 2 and by the simple kinetic treatment of the analytical data, further reaction of N-nitrosodiphenyl-
The chromatographic studies have brought to light some interesting relations between the structures of the compounds and their chromatographic properties on silicic acid. Table I1 records tbe relative chromatographic positions of a number of derivatives of diphenylamine. It is evident that the position of a nitro group has a marked effect on the relative adsorption affinity. Thus, 2-nitrodiphenylamine and 4-nitrodiphenylamine are both more strongly adsorbed than diphenylamine, but the former is only slightly more so. This effect of a 2-nitro group is so marked t h a t even when a second nitro group is present as in
TABLE11. RELATIVECIIRODISTOGRAPHIC POSITIONS OF DERIVATIVES OF DIPHENYLAMINE AND RELATED COMPOUNDS O N SILICICACID-CELITEO 4-Nitrosodiphenylarnine b 2,2’,4,4’,6,6’-Hexanitrodiphenylamino Picric acid 2,2‘,4,4’ 6-Pentanitrodiphenylamine 4,i’-Dinitrodiphenglaminec 2,2’,4,4’-Tetranitrodiphenyla1nine 2,4,4’-Trinitrodiphenylamine 2,2’,4-Trinitrodiphenrlamine ,V-iG t,roso-2.4’-dinitrodiDhenvlaxnine -4-Nitrodiphenylarnine .~ S-Nitroso-4,4’-di1iitrodighRnpiarr line 8,4‘-Dinitrodiphenylamine N-Nitroso-2-nitrodiphenylamixie S,N’-Diphenylbenzidine 2,4-Dinitrodiphenylatnine 2,2’-Dinitrodiphenylamine N-Xitroso-4-nitrodiphenylamined 1V-NitrosodiphenyIa.mine e 8-Sitrodiphenylamine Diphenylamine
Tetraphenylhydrazinc I n t h e order of decreasing adsorption affinity. T h e top four compounds were developed with polar solvents such as acetone in ligroin, t h e others with decreasing ratios of benzene in ligroin. 0 Position is uncertain; perhaps i t should be higher. d When ether-ligroin 19 the developer, nitroglycenn is above this compound e %;hen benzene-ligroin is the developer, nitroglycerin is between AVnitrosodiphenylamine a n d 2-nitrodiphenylamine. a b
December 1949
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INDUSTRIAL AND ENGINEERING CHEMISTRY
2,2’-, 2,P, and 2,4’-dinitrodiphenylamine the compounds are less strongly adsorbed than 4-nitrodiphenylamine, and correspondingly, the tri- and tetranitro compounds are less strongly adsorbed than 4,4’-dinitrodiphenylamine; chelation of the 2nitro group and the amino group probably is the cause of this effect. Introduction of a n N-nitroso group may either increase or decrease the affinity of the compound relative t o the parent substance. For example, comparison of the nitroso derivatives of 2-nitro- and 2,4’-dinitrodiphenylamine and 4-nitro- and 4,4’dinitrodiphenylamine with the parent compounds again shows the influence of the 2-nitro group. T o chromatograph successfully the compounds listed in Table 11, i t was necessary t o decrease the proportion of benzene in the developer for the compounds with lesser affinity. However, these changes in the proportion of the solvents in a given developer caused no inversions in relative position although inversions were noticed when the type of developer was changed. The different position of nitroglycerin when developed with ether-ligroin and benzeneligroin is evident.
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after such an extraction was rarely colorless, but essentially all of the color (if the samples had been heated for only a few days) could be removed if the residue was dried and then extracted with methanol for 2 hours in a Soxhlet apparatus. The pigments thus extracted were finally dissolved in a 2% solution of acetic acid in ethyl acetate. Extraction with methanol succeeds only if the nitrogen content of the nitrocellulose is high enough t o prevent gelatinization. MATERlALS
Most of the studies of the transformation products of diphenylamine were made on portions of a commercial lot of American Ballistite JP 204 which had been manufactured by the slurry process, I t s specifications follow: nitrocellulose 51.60% (13.2% nitrogen), nitroglycerin 43.00, potassium nitrate 1.40, diethyl phthala t e 3.25, diphenylamine 0.75, and methylcellulose (added) 0.16%.
The adsorbent was a mixture of Merck reagent-grade silicic acid and Celite 535 (Johns-Manville Corporation) in the ratio of 2 to 1 or 4 t o 1 by weight. Efficient mechanical shaking for 30 minutes produced a homogeneous mixture. Both new and reclaimed adsorbent were used; the adsorbent may be reclaimed merely by allowing the solvents with which it is wet-for example, after elution-to evaporate in air. Different lots of Merck reagent silicic acid show variations in adsorptive strength, and furthermore, reclaimed adsorbent is stronger than new material; consequently, quantities of developer which are given below for the various separations would probably require some modification before the separations could be repeated. Solvents, with the exception of the absolute ethanol which was used for spectrophotometry, were distilled without fractionation through an all-Pyrex still. Ligroin of various bdiling ranges was used: 28Oto 38” C. (Skellysolve A), 30” to 60” (Skellysolve F), and 60” to 70” (Skellysolve B). Other solvents were good grades of benzene (not thiophene-free), absolute ether, absolute ethanol,
Samples used for heating were in the form of 1-inch lengths of a grain which was 1.7 inches in diameter with a 0.6-inch perforation and which had been prepared by solventless extrusion; the weight of each was about 50 grams. The powder was stored in individual vented metal cans in a n electrically heated oven at 71 f 2 C. Before the chromatographic separation of the derivatives of diphenylamine could be accomplished, it was necessary to separate them and the soluble constituents of the powder from the insoluble nitrocellulose and potassium nitrate. Accordingly, a sample of the powder in the form of 0.15-mm. slices which had been prepared with a sliding microtome was extracted in a Soxhlet apparatus for 3 hours with methylene chloride. The solvent was then evaporated, and the residue was taken up in a volume of solvent or solvent mixture appropriate to the particular determination. The residue of nitrocellulose which remained
acetone, ethyl acetate, acetic acid, methylene chloride, and methanol. Streak reagents which were used for the detection of colorless zones were prepared as follows: “nitrous acid reagent” was a 1% solution of C.P. sodium nitrite in concentrated sulfuric acid, “diphenylamine reagent” was a 1% solution of recrystallined diphenylamine in concentrated sulfuric acid, “sodium hydroxide reagent” was a 6 N solution of C.P. sodium hydroxide. Samples of nitro and nitroso derivatives whose presence in heated powder was anticipated were prepared t o aid in the identification of the isolated derivatives. If the compounds were not available commercially, they were made by methods which would lead unambiguously to the desired product. Table I11 lists methods of preparation, melting points, and some essential spectrophotometric properties of these derivatives.
OPERATIONS ON SMOKELESS POWDER PRIOR TO CHROMATOGRAPHY
4
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against the edge of a table alternation of the two method. was advantageous. Spectrophotometrio D a t a Each column was prewashec, Positiond C/D, before the chromatogram wab of max. mg./ PO0 ml. in abs. run in order to remove im R.I.P., 0 c , alcohol, for &’’~&~ X purities which interfered witk 10-V Citation for Method of Preparationa Literatureb 0bsvd.e Compound my P rm-8 spectrophotometric deterniina 52 8-54 1 53 285 0 835 2.03 Diphenylamine tion in the ultraviolet region (DPN LeRosen ( l a ) , Schroeder ( 2 2 ) 66.5-67.6 66.2-66 8 295 3.50 0.59 &T-lyitroso-DP.4 143-144.6 145.4-146,6 421 0.72 4-Nitroso-DPA 2.75 and Trueblood and Malm422 3.24 0.66 2-Nitro-DPA 75-75.5 74.9-76.0 berg ( 2 5 ) have discussed the 132-133 135-135.5 4-Nitro-DP A 390 1.01 2.12 effect of prewashing upon tht adsorptive properties of silicic acid. The preffashing, with H N-Nitroso-299-100 98.1-98.8 liane ,* ~, few exceptions, was made \+it1 nitro-DPA 127-1328 K-Nitroso-4Same procedure as for ,V-nitroso-2- 130- 134 317-20 1.78 1.37 V ml. of ether and 2 V ml. 0’ nitro-DPA; never heated above nitro-DPB room temp. (25, I ) ligroin (60’ to 70’ C.); the tern, 2,2‘-Dinitro166-169 172 1-172,5 417-23 2.76 0.94 (9, 17) “17 mLY’is defined as the volDPA 157.3-158 349-51 1.52 2,4-Dinitro-DP.4 Eastman White Label, recrystd. 156-159 :,70 ume of solvent which is re from hot CHCls by pouring into 8 vol. of E t O H ; (3, Vol. XII, p. quired to wet completely (3 751) column of adsorbent ( 2 2 ) . The 219-223 224-224.4 2,4’-I)initro405 1.86 1.39 DPA composition of solvents rtntl 214-216 217.6-218.2 4,4’-Dinitro402 0.69 8.75 (16;. 3 , Vol. XII, p. 716) Similar t o method of Wielaiid a n d Noneh 1.655167 311-12 1.93 1.49 DPA developers is expressed in term. Lecher ( 8 6 ) : recrvstd. from 1t o 1 (decompd.) N-Nitroeo-2,4’of the ratios of the volume& dinitro-DPA dioxane-water a? room temn. ,V-Kitros0-4 4‘150-189 154-156 308-10 1,60 1.80 of their constituents. Often it (decompd.) (decompd.) dinitro-DPA 183--186 187.5-188.1 370-75 2.13 1.43 2,2’,4-Trinitrowas desirabk to postwash the DPA column with 1 to 1.5 T‘ mi 181-189 190--190.8 2,4,4‘-Trinitro365-67 1.41 2.16 DPA of ligroin (28’ to 38’ or 30’ 203.3-204 401-02 1.54 2,2’4,4‘-Tetreni- Obtained from Russell McGill, 199 2.27 tro-DPA Bur. Mines; recrystd. f r o m aceto 60” C.) in order to removt tone a n d ligroin; (3,Vol. XII?p. the solvents with which thi 7x2) 2,2’,4,4’,6-Penta- ( 8 ) 196-197 197 7 - 1 9 8 , 8 391-935 2.09 1.89 column was wet, because these nitro-DPA 376-79P 243-244.5 242.5-244.5 2,2’,4,4’,6,6‘(6) 2.58 1.70 solvents sometimes interfered Hexanitro-DPA (decompd.) (decompd.) with reagents for the detectioi Gen. Chem. Co. reagent picric acid 122.5 357-59; 122.5 1.63 1.40 Picric acid recrystd. from water; (3,‘Vol. V I , of colorless zones p. 267) 59% 0,72 7.7 DPAblue ( N , N ’ , ( 1 4 ) After each chromatogrmr N”-tripheny! had been developed. the zone pararosaniline hydrochloride) if colorless, was detected b\ a T h e first literature citation under each compound is t o the method of preparation; melting points of the conistreaking the column uith a11 pound are also given in other references. b Melting points within these extremes are stated in t h e literature; these values are not usually those of a n y appropriate reagent. To avoid given preparation. loss of zone when the streakCalibrated thermometers were used and stem corrections were applied. d Other maxima are usually t o be observed in the spectrum, b u t t h a t given is convenient for spectrophotometric ing reagent was removed befort determination. 6 C = concentration in mg. per 100 mi.: D = log ( I o / I ) *where D = optical density, Io = intensity of incident elution the column was streaked Light, a n d I = intensity of transmitted light. from top and bottom until d Molecular extinction coefficient: E??h _”.... = log ( I o / I ) / l c ~where 1 = length of solution traversed a n d c = conaentration in moles per liter. the limits of the zone wert 0 Compound softens a t 1 2 7 O a n d melts a t 132’ C. detected; the streak was never A Compound apparently has been prepared, b u t no melting point is given in literature. i Solution was acidified with one drop of concentrated hydrochloric acid per 100 ml. continued through the zont I Solution was made alkaline with one drop of 12 N sodium hydroxide per 100 ml. if quantitative recovery was ‘ desired. JT7ith corrosive reagents i t is advantageous t u iPPARATUS AND METHODS allow the reagent t o flow from a dropper down a thin glass rod onto the column rather than t o use a brush. The desired zone+ The chromatographic tubes were of the type designed by Zechwere then cut from the column, made into a slurry with eluent meister and Cholnoky (28). For elution, Pyrex funnels of Buchand eluted. Ether was the eluent unless specified otherwise ner type which had fritted disks of medium porosity were used. The eluent was evaporated under reduced pressure a t 40” C The packing of columns of silicic acid-Celite did not require a few milliliters of the solvent in which the residue was t o an elaborate procedure. After the chromatographic tube had be dissolved were added and evaporated, and the residue was been set up on a filter flask, suction (of a water aspirator, for taken up in the desired solvent. If spectrophotometric examinaexample) was applied and the dry adsorbent was poured slowly tion was to be made, the residue was taken up in absolute alcohol into the tube and permitted to settle into an evenly packed and diluted to an appropriate volume. IC I echomatograph! column. Since th’e particles do not cling together, a tightly was necessary, the residue was taken up in the desired solvmt packed upper surface cannot be formed; the surface was, howand rechromatographed. ever, carefully smoothed. Suction was applied throughout the Derivatives of diphenylamine which were isolated from course of the chromatographic experiment. smokeless powder a e r e identified by several means-chromatoExtrusion of columns of silicic acid was occasionally difficult but could almost always be accomplished. After the chrographic properties, reactions on the column t o various reagento, matogram bad been completed and the solvents had drained from and spectrophotometric properties. The compounds described the column, the top section of the tube was removed, inverted, in Table I11 were prepared; their chromatographic properties with several developers, reactions toward sodium hydroxide and and then tapped against the top of a table until the column had moved a few millimeters, and, if necessary, the side was rapped nitrous arid, and spectra in the visible and ultraviolet region9 TABLE111. METHODS O F P R E P 4 R A T I O N , MELTINGPOINTS, AND SPECTROPHOTOMETRI@ PROPERTIES OF SITRO AKD NITROSODERIVATIVES OF DIPHENYLAMIKE
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INDUSTRIAL AND ENGINEERING CHEMISTRY
were determined before a study of smokeless powder was made. As the aging of the powder progressed, derivatives which had not been present in the preceding samples were detected on the column and first identified by chromatographic behavior and color reactions, but the final burden of identification was placed on spectrophotometric properties. The spectrophotometric data of Table I11 are sufficient for the quantitative determination of a, compound if the substance has been identified but are not adequate for identification. However, even closely related derivatived have sufficiently unique spectra so that identification of the compound by comparison of the entire spectral curve with that of known compounds is unambiguous; the spectral curves of these compounds will be published in a separate paper. Few of the compounds which were isolated from powder were identified by melting point. The spectrophotometric data in absolute ethanol presented in Table I11 were obtained with a Beckman quartz photoelectric spectrophotometer, Model DU. Samples of the compounds were dried in vacuo, in an Abderhalden dryer a t temperatures which depended upon the compound, weighed, and dissolved in absolute ethanol. Calibrated glassware was used to bring the solution to the proper dilution. Quartz cells were used, and the values of extinction were corrected for the deviation of the thickness of the cell from 1.000 om. and for the extinction of the solvent cell and solution cell relative to each other when both were filled with pure solvent. The spectrophotometric data for diphenylamine, N-nitrosodiphenylamine, and 4nitrodiphenylamine are believed to be accurate t o +0.5%; the data for the other compounds are probably accurate only to *2 or 3%. The recovery from the column after chromatographing was studied extensively for diphenylamine, N-nitrosodiphenylamine, a n d 4-nitrodiphenylamine as representatives of the various types of compounds which are formed in the powder. The recovery of these compounds was 100 * 2%. There is no reason to believe that the nitro derivatives should be difficult to recover since they are not labile compounds nor are they unusually strongly adsorbed, with the exception of the pentanitro and hexanitro compounds. The N-nitroso compounds are labile, and only for N-nitrosodiphenylamine and N-nitroso-4-nitrodiphenylamine can even roughly quantitative data be given. The composition of the powder in terms of the derivatives of diphenylamine is only roughly quantitative; 'it is probable that the values represent to within * 5 to 10% the over-all percentage of the compound in a given sample with the exception of the data for diphenylamine itself which are probably accurate to *2%. DISCUSSION OF TABLE I V
Some details of the chromatographic methods used for the separation of the derivatives of diphenylamine are given in Table IV. Although approximately twenty derivatives of diphenylamine were isolated from double-base smokeless powder, the problem of their isolation was simplified by the fact that no one sample contained all of the derivatives-for example, not all of the compounds which could be partially separated by operation 6 occurred in any one sample. However, their relative proportions differed much from sample t o sample. With few exceptions, each compound formed a well separated zone on the ahromatogram from which i t was eluted for spectrophotometric determination. The following paragraphs discuss difficulties which arose and precautions which were taken to ensure satisfactory results by the methods outlined in Table IV. In the determination of diphenylamine, 2-nitrodiphenylamine interfered when the diphenylamine was appreciably depleted because the two compounds could not be completely separated chromatographically. However, since the quantity of 2-nitrodiphenylamine was usually appreciably less than that of the diphenylamine, a correction was applied. The extinction of the eluate was determined a t 422 mp, a t which wave length 2-nitro-
2825
diphenylamine has a maximum but diphenylamine has no absorption. The maximum of diphenylamine is a t 285 mp, and a t this wave length the absorption of 2-nitrodiphenylamine is 1.5 times that a t 422 mp. Consequently, the extinction of diphenylamine in the mixture is the extinction a t 285 mp minus 1.5 times the extinction a t 422 mp. The simultaneous determination of 2-nitrodiphenylamine and diphenylamine was not possible because the extinction a t 422 mp under the conditions for the determination of diphenylamine is too small to permit accuracy. It was therefore necessary t o chromatograph separately a considerably larger sample of extract under the same conditions as for diphenylamine, to isolate the mixture, and t o determine the 2-nitrodiphenylamine a t a dilution which gave a satisfactory extinction a t 422 mp. N-Nitrosodiphenylamine is a labile compound, the estimation of which required much care. It was not permitted to remain in contact with the adsorbent any longer than necessary. The eluent was evaporated a t room temperature in vacuo, and the residue was then dissolved a t once in ethanol for spectrophotometry. Although the maximum in the spectrum of pure N nitrosodiphenylamine is a t 295 mp, the spectrum of material which was isolated by chromatography usually had a maximum between 290 and 295 mp; only if the position of the maximum was below this range was the determination unsatisfactory. Other N-nitroso derivatives required like precautions. In operations 1 to 4 diethyl phthalate is strongly adsorbed and, hence, well separated from the compound which was isolated in these operations. However, its presence was ignored in subsequent operations because i t is a colorless compound with an absorption maximum a t 275 mp; consequently, even if isolated with any of these colored compounds, i t would not interfere with the spectrophotometric determination. The separation of the more strongly adsorbed derivatives requires considerable rechromatography. The initial removal of nitroglycerin was advantageous since its presence in approximately fiftyfold greater amount than the sum of the derivatives tended to interfere with the separations. Subsequent treatment of the sections which were isolated in operation 6 was dependent on the type and proportions of the compounds which were present; operations 11 to 15 were designed to take care of various situations. Operation 7 did not completely separate the tetra- and pentanitro derivatives, and it was necessary to rechromatograph the interzone in order t o complete the separation. Although N-nitroso-2-nitrodiphenylamineand N-nitroso-4,4'dinitrodiphenylamine would occupy the same position on the column, no interference arose because both were never found in the same sample of powder. Furthermore, neither was ever present in more than minute quantity and the method for their determination is no more than qualitative. N-Nitroso-2nitrodiphenylamine was detected by rechromatographing section 6e on a column, 9 mm. in diameter, which had an 80-mm. layer of 2 to 1 calcium hydroxide-Celite on top of a 20-mm. layer of 2 to 1 silicic acid-Celite, and developing with 5 V ml. of 28" to 38" C. ligroin. The nitroso compound was washed through the calcium hydroxide and became adsorbed a t the top of the silicic acid where i t was detected by means of the purple color which i t produces with nitrous acid. Traces of the compounds in section 6d and 6f which may be present were retained by the calcium hydroxide. Evidence for the presence of N-nitroso-4,4'-dinitrodiphenylamine rests upon spectral changes which occurred when an eluate of the compound was permitted to age. The compound is labile and in solution decomposes to 4,4'-dinitrodiphenylamine; the spectral changes of eluates of section 6e from certain samples of heated powder indicated convincingly that the nitroso compound was present. There was similar but less convincing evidence that N-nitroso-2,4'-dinitrodiphenylamine (section 6 c ) was also present. The separation of 2,2'- and 2,4'-dinitrodiphenylamine (opera-
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Vol. 41, No. 12
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
tion 18) required several rechromatograms of 1% because of the tendency of 2,4'-dinitrodiphenylamine to form double zones ( 2 2 ) . If sodium hydroxide was applied t o the two zones which appeared when operation 18 was carried out, the upper produced a pale pink color characteristic of 2,4'-dinitrodiphenylamine, and the same color was produced in the upper portions of the lower zonp hut not in the lower portions which contain 2,2 '-dinitrodiphenylamine (the latter produces no color with sodium hydroxide). If the entire lower zone was rechromatographed, two zones appeared, but the color reactions of the upper part of the lower zone were less distinct and another chromatogram usually eliminated them entirely. I n addition to the described methods which were used for the isolation of the specified derivatives of diphenylamine, procedures mere also available for the detection of other derivatives which might be formed. Thus, an attempt was made to find 4-nitrosodiphenylamine, and if present, it would have been detected. Likewise, a search was made for possible oxidation products of diphenylamine, such as tetraphenylhydrazine and N,N' - diphenylbenzidine, but they were not detected. The blue, purple, and green compounds isolated in operation 20 are indicators, and their successful separation depended upon maintaining the acidity of the solution. The investigation of these substances was limited largely to spectrophotometric examination of their solutions under various conditions of pH. The compounds were isolated only from samples which had been heated for 5 days or less. When the acidic solution of the green compound in alcohol was neutralized, the color became brown and then colorless as an excess of alkali was added; likewise, the color of the blue material changed to red and faded t o yellow; the color of the purple zone disappeared on addition of alkali. A detailed comparison of the spectrophotometric and chromatographic properties of the blue substance and of diphenylamine blue (N,N',N''-triphenyl pararosaniline hydrochloride) has led
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December 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
2827
to the conclusion t h a t the cations of the two compounds are probably identical; in the powder the anion might be expected to be nitrate rather than chloride. The changes in color on the addition of alkali are the same as Tolbert, Branch, and Berlenbach describe for this type of dye (24). It has not been possible to identify the green and purple pigments. ACKNOWLEDGMENT
It is a pleasure to acknowledge indebtedness to Robert B. Corey under whose supervision the work was carried out, and t o Linus Pauling for many stimulating suggestions and continued interest. Albert 0. Dekker, Richard M. Lemmon, Rene S. Mills, Philip E. Wilcox, and M. Kent Wilson assisted in certain phases of the work. 9
LITERATURE CITED
N .
N
c
(1) Bamberger, E., Ber., 31,574, 581 (1898). (2) Becker, F., and Hunold, G. A., Z . ges Schzess- u. Spreng-
atofw., 33,a i 3 (1938). (3) Beilstein, “Handbuch der organischen Chemie,” 4th ed., 19181936. (4) Cook, S. G., IND. ENG.CHEM.,ANAL.ED.,7, 250 (1935). (5) Davis, T. L., “Chemistry of Powder and Explosives,” p. 185, New York, John Wiley & Sons, 1943. (6) Davis, T. L., and Ashdown, A. A,, IND.ENG.CHEM.,17, 6 7 4 (1925). (7) Davis, T. L., and Ashdown, A. A., J . Am. Chem. Sac., 46, 1054 (1924).
N . N
a
( 8 ) Duin, C. F. van, and Lennep, B. C. R. van, Rec. trav. chim., 38, 358 (1919). (9) (10) (11) (12) (13) (14) (15)
Eckert, A., and Steiner, K., Monatsh., 35,1154 (1914). Fischer, E., Ann., 190,174 (1878). Fischer, O., andHepp., E., Ber., 19, 2991 (1886). Fischer, P., Ibid., 24,3797 (1891). Goldberg, I., Ibid., 40,4541 (1907). Hausdoerfer, A., Ibid.,23,1963 (1890). Hewitt, J. T., Newman, S. H., and Winmill, T. F., J . Chem. Soc.,
95, 582 (1909). (16) Ikuta, M., Ann., 243,275 (1888). (17) Juillard, P., Bull. sac. chim., [ 3 ] 33, 1173 (1905). (18) LeRosen, A. L., J. Am. Chem. Soc., 67, 1683 (1945); 69, 87 (1947). (19) Matignon and Deligny, Compt. rend., 125, 1104 (1897). (20) Schmidt, O.,Ber., 36,2477 (1903). (21) Schomaker, V., unpublished data. (22) Schroeder, W. A., Ann. N . Y . Acad. Sci., 49,204 (1948). (23) Stoermer, R., and Hoffmann, P., Ber., 31,2535 (1898). (24) Tolbert, B. M., Branch, G. E. K., and Berlenbach, B. E., J . Am. Chem. SOC., 67,887, esp. 888, col. 2 (1945). (25) Trueblood, K. N., and Malmberg, E. W., Anal. Chem., 21, 1065 (1949). (26) Wieland, H., and Lecher, H., Ann., 392,166 (1912). (27) Witt, O., Ber., 8, 855 (1875). (28) Zechmeister, L., and Cholnoky, L., “Principles and Practice of Chromatography,” p. 62, Fig. 19, New York, John Wiley & Sons, 1943.
RECEIVED January 10, 1949. Contribution 1234, Gates and Crellin Laboratories of Chemistry. This paper is based in whole on work done for t h e Office of Scientific Research and Development under Contracts OEMsr-702 and OEMsr-881 with the California Institute of Technology. Some of t h e chromatographic problems associated with this work were presented before the “Conference on Chromatography,” New York Academy of Sciences, November 1946 ($3).
Correction
. .
2;No
I n the paper entitled “Di-tert-butyl Peroxide and 2,2-Bis(tert-buty1peroxy)butane” by Dickey, Raley, Bust, Treseder, and Vaughan [IND. ENG.CHEM., 41, 1673 (1949)l on page 1675 in Table I1 a t upper right, t l / 2 = 1.7( 10-20)e38~000 IRT should have been used instead of t l / z X 1.7(10~20)e33~000 IRT.
