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INDUSTRIAL AND ENGINEERING CHEMISTRY
the composition of the dew-poilit gas and bubble-point liquid from each of the two sources is given. The standard deviation between the two sets of data is 0.020 mole fraction for the gas phase and is 0.013 mole fraction for the liquid phase. ACKNOWLEDGMENT
contribution from American Petroleum lnThis paper is stitute Research Project 37,located a t the California Institute of Technology. Gordon Goff assisted with the experimental study and George Guill and Betty H. Kendall carried out the computations. LITERATURE CITED h
(1) Bridgernan, J . A m . Chem. Soc., 49, 1174 (1927). (2) Biidenholaer, Sage, and Larey, IND.END.~ I I E M . ,31, 369 (1939).
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(3) Dana, Jenkins, Burdick, H I I ~T i t n n l , Refrigerating E~zcI., 12, 387 (1926). Burks, J. Am. Chem. See., 49, 1403 (1927), (4) Keyes ( 5 ) ~~~l~~~and Gad&, I b & f , 53, 394 (1931). (6) Michels and Nederbragt, Physica, 3, 569 (1936). (7) Olds, Reamer, Sage, and Lacey, IND. ENQ.CHEM., 35, 922 (1943). (8) Reamer, Sage, and Larcy, Ibid., 41, 482 (1949). (9) Sage, Budenholzer, and Lacey, Ibid., 32, 1262 (1940). (10) Sage, Kennedy, and Lacey Ibid 28 601 (1936). 136 (11) sage and Lacey, Trans. fi,ining ,,,,et. 136 (1940). (12) Sage, Lacey, and Schaafsnna, IND.ENG.CHEM.,26, 214 (1934) (13) Sage, Lacey, and Sohaafsma, OiE Gas J.,32, No. 27, 12 (19331. (14) Sage, Schaafsma, and Lacey, IND.ENG.CHEM., 26, 1218 (1934) (15) Vold, J. A m . Chem. Soc., 57, 1192 (1935).
km. ynst.’
RICCEIVICD Julv 28. 1949. This is the 52nd . aaaer of a series A bibliograptiy . of the first 50 articles appears in IND. ENQ. CHEM.,41, 474 (1949); T h e 6 1 s t i s i n 1 ~ ENG. ~ . Casx.,41, 2871 (1949).
Chromatographic Investigations of Smokeless Powder DERIVATIVES OF CENTRALITE FORMED IN DOUBLE-BASE POWDERS DURING ACCELERATED AGING W. A. SCIIROEDER, M.KENT WILSON’, CHARLOTTE GR KEN, PHILIP E. WILCOX2, RENE S. MILLS, AND KENNETH N. TRUEBLOOD* California Institute of Technology, Pasadena 4, Calif.
Chromatographic-spectrophotometric methods have been used to study the derivatives that are formed from centralite (1,3-diethyl-1,3-diphenylurea)during the accelerated aging of double-base smokeless powder. Approximately 40 derivatives were isolated and about one half of these were identified. Quantitative determinations showed that the two types of powders which were studied differed in the nature of the main derivative produced: In the powder that initially contained only 1% of centralite, 4-nitrocentralite was the main derivative,
whereas in that which contained 9% of centralite, N nitroso-N-ethylaniline predominated. These compounds and other important derivatives were determined quantitatively in samples of aged powder; more than 30 isolated derivatives were present only in minor quantity. A scheme has been proposed to explain the formation of the identified derivatives from each other. Quantitative determinations showed that more than half of the original content of centralite reacted in an unknown manner, probably with nitrocellulose and/or nitroglycerin.
T
nitro derivatives of centralite. Masaki (16) and Moisak (17) have obtained analogous results. LBcorchB and Jovinet (13-16) first attempted to determine and explain the reactions which centralite undergoes in stabilizing a powder. They believed that centralite is only an inert constituent of the powder until decomposition of the major constituents, the nitroglycerin and nitrocellulose, has produced traces of acid; then, in proportion to need, the centralite is hydrolyzed to N-ethylaniline which reacts with nitrous acid to form N-nitroso-N-ethylaniline while any nitric acid yields, a t least in part, mononitrocentralite. LBcorchB and Jovinet were able to isolate N-nitroso-A*-ethylaniline from heated powder in appreciable amount, but their detection of a “nitrocentralite” is less convincing. Although they believed that N-nitroso-4-nitro-AT-ethylaniline was also a likely derivative, they admittedly had no evidence of its presence.
HE centralites, or 1,3-dialkyl-1,3-diphenylurcas,were initially used in the manufacture of smokeless powder as gelatinizers for nitrocellulose and as deterrents for progressive burning powders. [In accordance with the convention of ChemicaE Abstracts, the term “centralite” is used to refer to 1,3diethyl-l,3-diphenylurea. Davis (IO) discusses other usages. 1 In 1926 Apard ( 1 ) suggested that the benzene nuclei in the molecule should permit it to react with the decomposition products of a powder and hence to act as a stabilizer. His experiments showed that nitrogen dioxide reacts vigorously with centralite to produce a mixture of compounds and that nitric acid alone or in mixture with sulfuric acid yields well-defined dinitro and tetraI
Present address, Harvard University, Cambridge, Mass.
:Present address, Howard Medical School, Boston, Mass. 8
Present address, University of Cltlifornis at Los Angeles, Lo8 Angel&,
Calif.
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Apard ( 1 ) claimed to have detected tetranitrocentralite in heated powder by means of a color reaction with potassium hydroxide in acetone. Recently Parker (21, 22) and Ovenston and Parker (20) described experiments on the action of centralite as a stabilizer. Their experiments and those of the present authors were carried on concurrently during the recent war and each group was fully aware of the work and results of the other through official channels. Many of the conclusions which were drawn from the work described in the present paper are stated by Parker ( d l ) , although he offers no experimental evidence in support of them.
Centrolite 4-Nitrocentralite e 4,4'- Dinitrocentralite N-Nitroso-N-ethylaniline 0 N-Nitroso-4-n1rro-N-ethyIaniI1ne 0 2 , 4 - D i n i t r o - N - ethylaniline
0
B
0.6 0
TIME OF S T O R A G E AT 75. C.,WEEKS
Figure 1. Percentage of Centralite and Its Major Derivatives in Samples of RPL 142 after Accelerated Aging
The object of the present study was the determination, both qualitatively and quantitatively, of the derivatives which are formed when centralite acts as a stabilizer in double-base smokeless powder. Two types of powder were studied: One was a solventless-process cordite designated as JP 76, which originally contained about 9% of centralite in addition to nitrocellulose and nitroglycerin, and the other was a solvent-process powder designated as Radford pilot lot 142 of 1944 (RPL 142) which originally contained only about 1% of centralite. Artificial aging of both powders was produced by heating samples in vented metal cans a t 65' or 75" C. for varying periods of time up to 2 years. The derivatives of centralite were separated from each other and especially from nitroglycerin, the presence of which was the greatest hindrance to the work of LBcorch6 and Jovinet, by the application of chromatographic techniques to solutions which contained centralite, its derivatives, and nitroglycerin, all separated from the nitrocellulose by extraction of the powder. The quantitative determination of compounds that were isolated was made spectrophotometrically. OBSERVATIONS OF CHANGES IN HE4TED POWDER
Samples of the JP 76 were heated a t 65" C. and of the RPL 142 a t 65" and 75" C. During the heating, the appearance of the powders changed gradually from the original tan or light brown color to a more intensely brown and finally to a somewhat reddish brown. Loss in weight in the course of 6 months amounted to 2 or 3% and in the case of RPL 142 was not greatly influenced by the temperature of heating. KOcondensate appeared on the inside of the containers in which the samples were heated, in marked contrast to the behavior of double-base powders that contain diphenylamine as stabilizer (24). Although the heating of JP 76 was continued for 107 weeks at 6S", no sample evolved nitrogen dioxide. On the other hand, after 93 weeks a t 65" C., RPL 142 became blistered and actively produced nitrogen dioxide. At 75" C., three samples of RPL 142 which had been heated for 33 weeks behaved differently: One fired at this time,
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a second became blistered and evolved nitrogen dioxide, and a third was unchanged in appearance (except for color) even after 41 weeks. RESULTS OF QUALITATIVE ANALYSES
When the chromatographic methods, detailed below, were applied to selected samples of both JP 76 and RPL 142, it was possible to isolate approximately 40 compounds in varying degrees of purity. Of these compounds, 17 were identified, 3 were tentatively identified, and the remainder could not be recognized. In the following list of identified substances which probably were derived from centralite, all were determined quantitatively, but those not italicized together accounted for no more than a few per cent of the centralite originally present: 2-nitrocentralite, &nitrocentralite, 4,4'-dinitrocentra2ite, 2,4,4'trinitrocentralite, N-nitroso-N-ethylaniline, 2-nitro-.VV-ethy1ani2,4line, 4-nitro-~V-ethylaniline, i~-nitl.oso-4-nitro-!~-eth~~~n~~~ne, dinitro-N-ethylaniline, N-ethylcarbanilide, 4-nitroaniline, and 4-nitrophenol. Certain ot,her identified compounds-namely, 4-nitro-A-,N-diethylaniline and several derivatives of diphenylamine-probably were derived from traces of iV,N-diethylaniline which can be detected in commercial centralite and from tracas of diphenylamine which were accidentally introduced during manufacture. The three compounds that were ident,ified tentatively were probably degradation products of nitroglycerin, for t'hey were similar to substances which can be isolated from old solutions of nitroglycerin. Although only the italicized compounds in the above list could be isolated in appreciable quantity from the powder, it is, nevertheless, possible that the reactions could have passed t.hrough one or more of the minor products if the reaction rates were sufficiently different. Dinitrocentralite and dinitro-N-ethylaniline were present in RPL 142 but not in J P 76; however, their presence in the latter is hardly to be expected, because the react'ions, even in samples of this powder which had been heated for 2 years, had not proceeded to the point a t which their formation was likely. Among the minor derivatives, 4-nitroaniline was found only in J P 76, and 2-nitrocentralite and 2-nitro-Nethylaniline were detected only in RPL 142. Most of the approximately twenty unidentified compounds that were isolated probably had st'ructures that represented appreciable fragments of the original centralite molecule. This conclusion is based upon the fact that all but a few possessed definitive absorption spectra in the near ultraviolet region, a feature which they would be unlikely to have unless a t least one of the benzene nuclei of the centralite molecule was still present. The characteristic spectra of these compounds were compared with those of a large number of possible derivatives which had been prepared, but identification was not possible. However, a very rough estimate of the quantity of the unidentified compounds could be made by assuming that each contained a significant fragment of the centralite molecule and that accordingly their quantitative spectrophotometric characteristics were similar to those of the many possible derivatives that were available. On the basis of these assumptions, it was estimated that the total quantity of the unidentified compounds probably was only 2 or 3% of the original content of centralite. Accordingly, it may be concluded that these substances are of minor significance and that the fact that not all of them were found in both JP 76 and RPL 142 is unimportant. An attempt to f a d N-ethylaniline in the sample of RPL 142 which had been heated a t 75' for 4 weeks showed that if any was present its quantity was less than 0.06 mg. in 10 grams of powder. Although no special search for N-ethylaniline was made in other samples, it is improbable that more than traces could have been present, because the chromatographic and spectrophotometric properties are such that its presence in appreciable amount would have interfered with the determination of N-nitroso-Nethylaniline.
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541
in method of m a n u f a c t u r e (JP 76 solventless processed, RPL 142 solvent processed), hrNNitroso-42,4in nitrogen content of the niTime of 4,4'Nitroso- nitro-NDinitroCentralite trocellulose (JP 76,12.2%,RPL Storage, 4-NitroDinitroN-ethylethylN-ethylAccounted Weeks Centralite centralite centralite aniline aniline aniline for, %" 142: 13.2%), and in physical At 65' C. dimensions (see Table IV). All 0 0.95 0.01 ... ... ... 100 1 0.91 0.04 ... T;&e .. .. .. ... 98 evidence indicates that the im2 0.83 0.07 ... 0.03 96 4 0.73 0.08 ... 0.04 ... 87 portant factor is the percentage 9 0.57 0.13 ... 0.05 ... ... 77 of centralite and that the other 13 0.44 0.17 ... 0.07 ... 67 20 0.38 0.17 . . . 0.08 0.02 ... 64 differences are relatively un37 0.12 0.29 ... 0.05 0.07 ... 48 0.30 ... 0.00 0.11 34 important. Thus, a powder 51 0.00 60 ... 0.19 0.02 .... .. 0.15 Trace 29 which contained 1% of central78 ... 0.03 0.15 0.15 Trace 24 91 ... 0.00 0.11 ... 0.10 0.03 18 ite, which was manufactured 93b (normal end) .. .. .. 0.04c .. .. .. 0.06 0.07 11 93b (blistered end) TraceC 0.00 0.05 3 in these laboratories by a solAt 75O C. ventless process, which con0 0.95 0.01 ... ... ... ... 100 tained nitrocellul~oseof 12.6% 1.5 0.74 0.10 ... 0.03 ... 89 4 0.46 0.20J ... 0.05 0.01 ... 71 nitrogen content, and nhich 9 0.13 0.31 ... 0.07 0.03 ... 60 12 0.00 0.33 ... 0.03 0.07 ... 38 was in the form of 0.25-inch 16 ... 0.29 0.02 0.00 0.10 ... 35 rods behaved like RPL 142 in 22 ... 0.09 0.16 ... 0.13 30 26 ... 0.05 0.21 ... 0.11 +&e 30 the rate a t which the central32 e ... 0.05 0.14O ... 0.04 0.08 25 was and in the 5 Percentage of original centralite that can be accounted for in form of centralite and its known derivatives. In oelculations it was assumed that two molecules of each product which contains only one benzene nucleus were proformation of Cnitrocentralite duoed from one molecule of centralite. as the main derivative. This b At this time one end of sample began to evolve red fumes and assumed a blistered appearance. 0 Traces of 2,4,4'-trinitrocentralite were resent. powder resembled RPL 142 in d Amount of 2-nitrocentralite was rough& 6% of that of 4-nitrocentralite in this and succeeding samples. e Sample began to evolve red fumes several weeks after removal from ovens. content of centralite, JP 76 in method of manufacture and nitrogen content of nitrocelThe qualitative analyses were made on samples of powder lulose, and neither in physical dimensions. which had originally contained about 100 mg. of centralite, and St 65' C. the rate of reaction of centralite in JP 76 is about five chromatographic-spectrophotometric methods can detect and times that in RPL 142. However, because of the greater initial determine (at least roughly quantitatively) less than 0.1 mg. of amount of centralite in JP 76, the reactions were not as far adsubstances of this sort. Hence, the possibility of overlooking vanced as in RPL 142; thus, after about 2 years of heating, derivatives which were present in significant quantity is remote. N-nitroso-4-nitro-N-ethylanilinewas increasing in amount in JP 76 but had been exhausted in RPL 142. Other differences RESULTS OF QUANTITATIVE ANALYSES may be noted by comparison of Tables I and 11. In RPL 142 the change of temperature from 65" to 75" C. The major derivatives of centralite, which were detected in the was instrumental mainly in increasing the rate of the reactions. qualitative analysis, were determined in a series of samples of There were only minor changes in the relative proportions of the RPL 142 which had been heated a t 65" or 75" C. for varying various derivatives and the percentage of centralite accounted for lengths of time and in a series of samples of JP 76 which had been was essentially the same a t equivalent stages of reaction, heated a t 65' C. The results of these determinations, which were made with an accuracy of *5 or lo%, are given in Tables FATE OF CENTRALITE UNACCOUNTED FOR I and 11. Figure 1 illustrates the increase and decrease in the The data in Tables I and I1 show that, as the time of heating percentages of the major derivatives in RPL 142 during storage at increases, less and less of the original content of centralite may be 75" c. LBcorchB and Jovinet were able to identify N-nitroso-Ifethylaniline as a derivative of centralite in heated powders and TABLE 11. PERCENTAGE OF CENTRALITEAND ITS MAJOR to obtain some measure of the quantity of this derivative in the DERIVATIVES IN SAMPLES OF CORDITE J P 76 AFTER STORAGE AT powder by indirect methods. The chromatographic methods of 65" C. Centralite the present study have permitted the direct isolation not only Time of N-Nitroso- Accounted of those derivatives which LBcorch6 and Jovinet postulated (NStorage, N-Nitroso-Ai- 4-Nitro- 4-nitro-Nfor, Weeks Centralite ethylaniline centralit,e ethylaniline %" nitroso-N-ethylaniline, nitronitroso-N-ethylaniline, and nitro0 8 . 3 5 b , 8 . 8 6 . . . 100 c centralite) but also of a host of others, most of which are present 8.40 1 0.05 2 8.34 0.08 0 :0 2 d ... in minor amount. In conjunction with spectrophotometry, the 8.21 0.09 ,.. chromatographic isolation has made possible the quantitative 7.80 0.18 94 7 . 4 3 8 0.28 . , . . .. determination of the important derivatives and has shown that 6.92 12 0.43 ... 6.63 16.3 0.52 .., ... oentralite reacts very differently in the two types of powder that 6S.57,3;8e .03,6.28 21 0.74,0.7e 0.06 ... 81 were studied. Moreover, the quantitative determinations of the 36 1.15,1.2' 0.07 ... 1.1' 52 3.2 ... Trac'e e 50 major identified derivatives have shown that for the most part 1.6: 72 1.4e ... 0.09e ... 93 0.6 1.348 0.148 O.OBe the reactions of centralite follow entirely unknown paths. 23 TABLE I. PERCENTAGE OF CENTRALITE AND ITSMAJOR DERIVATIVES IN SAMPLES OF RADFORD PILOT LOT142 AFTER STORAGE AT 65" AND 75" c.
I . .
. I .
2,-
...
DIFFERENCES IN BEHAVIOR OF JP 76 AND RPL 142
There are marked differences in the type of derivative which is formed directly from centralite in JP 76 and RPL 142: In JP 76, N-nitroso-N-ethylaniline is the main known derivative and 4nitrocentralite is present in minor quantity, whereas in RPL 142 the situation is reversed. These powders differ in four ways: in content of centralite (JP 76 about 970,RPL 142 about l%),
ca. O . l e 107 0.85e 0.23e See a Table I. b The& analyses of unheated cordite were made on separate ether extracts of portions of different graiui. As each was reproducible, i t appeam that discrepanoy must be real. C Initial content of centralite assumed to be 8.5%. Because of contamination by a n unknown compound that could not be separated from 4-nitrocentralite, percentage as given is probably slightly greater than actual 4-nitrocentralite content. Contaminant was not present in RPL 142. e Results obtained with methylene chloride as extracting agent; all other values measured on ether extracts. Q
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accounted for in the form of identified derivatives. That not only centralite but also its known derivatives undergo unknown reactions is indicated by the continued losses after the exhaustion of centrslite. During the period when centralite is still present much of the centralite accounted for is simply unreacted centralite. Because most of the centralite is not converted into known detectable compounds, much attention was given to the problem of accounting for its disappearance. Consideration was given to the possibility that the "missing" centralite may volatilize in the form of centralite or its derivatives, may be present as undetected derivatives in the extract, and/or may be present in the nitrocellulose residue which remains after extraction. VOL.4TILIZATION O F CENTRALITE ATZD/OR DERIVATIVES. Apard (2) stated without citing experimental data that centralite volatilizes appreciably during the heating of powder. As has already been mentioned, a loss in weight of 2 to 3% does occur on heating; consequently, loss by volatilization must be given serious consideration.
To determine the nature of the compounds that might thus be lost, samples of both JP 76 and RPL 142 were heated for 2 weeks a t 75" C. (in separate experiments) in all-glass apparatus similar to an Abderhalden dryer, through which was passed a stream of dried preheated air a t the rate of 10 ml. er minute. From the heating chamber the air was led throug! two consecutive allglass traps which were cooled in a bath of methylene chloride and dry ice. The material which had condensed in the line to the traps and in the traps themselves was then combined and analyzed by chromatographic-spectrophotometric methods and in other appropriate ways. The results of these experiments are summarized in Table 111. TABLE111. VOLATILIZATIOS O F CENTRAUTE AND ITSDERIV.4TITES FROM SMOKELESS POWDER DURING STORAGE AT 75' c. FOR 2 mTE1SKb
RPL 142 JP 76 Weight of sample, g. 37.909 39,970 47 1 Loss i n weight during heating, mg. 424 476 426 Weight of distillate mg. 52 Weight of material'uncondensed, mg. 45 Analysis of distillate, mg. a 207b Water Xitroglycerin 188 166 2 4 Centralite Trace 5 iv-nitroso-N-ethylaniline Unknown derivatives (approx.) 3 3 31" 41 Unaccounted for Analysis of powder, mg. Centralite Before heating 360 3485 Bfter heating 220 3258 4-Nitrocentralite 4 0 Before 53 0 After A'-Ni troso-A'-e thylaniline Before 0 0 Trace 80 After \Yeight of centralite reacted durino hentino, rn6. 140 227 Weimht of centralite accounted is by derivatives in pok.der and distillate, mg. 45 a2 a By analogy to JP.76 quantity of water in distillate is assumed to bo 200 mg. Hence, by difference, amount unaccounted for is 31 mg. b Determined by titration with Karl Fischer reagent according to procrdure of Smith, Bryant, and hIitchell ( 2 6 ) .
...
Despite the ninefold difference in the rentralite content of the powders and despite the fact that RPL 142 was prepared by a solvent process and JP 76 by a solventless process, the two powders m r e almost identical in behavior in this experiment. Most of the loss in weight (about 1%) which occurred in both powders was due to vaporization of watei and nitroglycerin. Although small amounts of centralite, A'-nitroso-N-ethylaniline, and unidentified compounds were present in the distillates, the volatilixation of centralite itself, or of easily recognizaJe fragments, was inappreciable Then compared to the amount of centralite that had reacted during the heating. A noteworthy feature of the results is the fact that more than 10% of the material which was volatilized during heating apparently either was uncondensed a t the temperature of dry ice or a a s so volatile a t room temperature that it distilled away com-
Vol. 42, No. 3
pletely before the traps could be weighed after they had been allowed to come to room temperature. When the traps were opened after they had reached room temperature, it was evident from the odor that volatile compounds of some kind, perhaps aldehydes such &s acetaldehyde or acrolein, were present in the condensate from each type of powder. The serious fragmentation of centralite which must occur to produce such known derivatives as 4-nitroaniline and 4-nitrophenol makes it not unreasonable that compounds of low molecular weight should be produced simultaneously. Under similar conditions the weight of distillate from ti powder which contained diphenylamine was equal to the loss in weight of the powder (24). However, because the diphenylamine powder was heated at 71 C. for only 4 days, the differences may not be significant. I t should not be inferred from the present discussion that cenlralite is the sole possible source of the uncondensed fraction; certainly the possibility that nitroglycerin and/or nitrocellulose may also be responsiblc for the volatile material cannot be ignored. An appreciable fraction (8 to 10%) of the material in the distillates could not be identified. When each distillate was analyzed, a careful search was made for unknown compounds, but only about 3 mg. could be detected. Whatever the undetected remainder may be, it must be very weakly adsorbed or react with none of the reagents which were applied to the column and hence must retain less of the structure of centralite than N-ethylaniline. Here again the source of the substances may be nitroglycerin and/or nitrocellulose. The conclusion may be drawn that volatilization of centralite and its known derivatives is unimportant but that some rather volatile fragments are produced during the reactions of centralite and/or of nitroglycerin and nitrocellulose. PRESESCE O F UNDETECTED DERIV.4TIVES I N EXTRACT. AIthough chromatographic-spectrophotometric studies of the extracts of both JP 76 and RPL 142 failed to reveal the presence of any appreciable quantit'y of undetected derivatives, nevertheless, the possibility could not be excluded that one or more compounds with unexpected properties vrere present in these extracts. In order to obtain evidence for or against this possibility, the weights of the extracts of about 10 samples of heated and unheated powder which were represcntative of JP 76 and RPL 142 Tyere compared with the sum of the weights of the k n o m constituents of each extract. The results from RPL 142 were inconclusive because so much of the weight was nitroglycerin; the uncertainties in the method for its determination mere of the order of the differences that were being sought. This factor was not important in the study of extracts of JP 76 because of the larger proportion of centralite to nitroglycerin, but other difficulties made definite conclusions doubtful. Among these difficulties was the uncertainty introduced by the slight solubility of nitrocellulose in the extracting solvent,, methylene chloride. It seemed that significant amounts of undetected substances were not present in the extracts, but this conclusion could not be subst'antiated by unequivocable data. PRESEXCE OF DERIVATIVES IN XITROCELLULOSE RESIDUE. The most obvious change which occurs when centralite-containing powders are heated is the gradual increase in intensity of the original tan or brownish color. Yet when the powder is exhaustively extracted with ether or methylene chloride, the color of the remaining nitrocellulose is essentially the same a s that of the powder before extraction. This fact led to the conclusion that the most probable fate of the centralite unaccounted for i n some way involved the nitrocellulose. If the centralite has been transfornied into subst,ances which are merely insoluble, or are strongly adsorbed on the nitrocellulose, it should be possible to obtain information by using a different extracting solvent or by dissolving the entire residue and perhaps then destroying the nitrocellulose chemically. On the other hand, if the compounds are bound chemically to the nitrocellulose, the most practical procedure would seem to be to destroy
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INDUSTRIAL AND ENGINEERING CHEMISTRY
the nitrocellulose in some way that would permit the recovery of the derivatives in recognizable form. When extraction with solvents such as water and dioxane failed to give positive results, recourse was had to methods that destroyed the nitrocellulose. Decomposition with alkaline sodium peroxide or with concentrated nitric acid gave encouraging results, but hydrolysis with acid or reduction with ferrous chloride yielded no information of value. After a sample of JP 76 which had been heated for 93 weeks at 65" C. had been exhaustively extracted, 1 gram of the nitrocellulose residue was decomposed with alkaline sodium peroxide; I O mg. of centralite, 0.3 mg. of l-ethyl-3-phenylurea, 0.25 mg. of 4-nitroaniline1 and 0.05 mg. of 4-nitro-N-ethylaniline were isolated from the resulting reaction mixture. Certainly, the quantities are insignificant, because the powder which is equivalent to I gram of nitrocellulose originally contained 160 mg. of centralite, three fourths of which is unaccounted for, but the result does show that the residue contains derivatives which even exhaustive extraction does not remove. Destruction of the nitrocellulose by means of nitric acid with accompanying drastic alteration of derivatives of centralite was accomplished by a method which was essentially that of Cook (8) for the determination of '[total diphenylamine'' in aged diphenylamine powders. One gram of exhaustively extracted nitrocellulose from the sample of JP 76 which had been heated for 93 weeks at 65' C. yielded 7 to 12 mg. of picric acid in various experiments. The quantities were not greatly altered by variations in the procedure. Because the picric acid could be formed only from centralite or its derivatives, it seemed that valuable information could be obtained b y studying the extent of conversion of various compounds in the presence of 1 gram of unheated nitrocellulose. The extent of conversion was as follows: centralite, less than 1%; A'-nitroso-AT-ethylaniline, 30%; l-ethyl-3-phenylurea, 47%; arid picric acid, 95%. The 95% "yield" of picric acid shows that the entire procedure is adequate and that picric acid, once formed, is not destroyed. Unquestionably, the yield depends greatly upon the structure of the starting material. Hence, although 12 mg. of picric acid (equivalent to about 6 mg. of centralite) represent only about 5% of the centralite which is unaccounted for in this particular sample, the unquantitative conversion of various derivatives indicates that considerably greater amounts of derivatives may actually be present in the residue. In view of these results, the nitrocellulose residue appears to be the most probable location of the major portion of the centralite which is unaccounted for, but there is no evidence as to the form in which it may be. SCHEME FOR FORMATION OF IDENTIFIED DERIVATIVES
The parent compound of certain identified derivatives of centralite in smokeless powder is clearly evident: Thus, in all probability, N-ethylcarbanilide, 2-nitrocentralite, and 4-nitrocentralite are derived from centralite; 4,4'-dinitrocentralite from 4-nitrocentralite; and trinitrocentralite from dinitrocentralite. However, N-nitr~so-~V-ethylaniline,N-nitroso-4-nitro-N-ethylaniline, and others which result from the splitting of the molecule may have several sources. In order to determine the main reactions which each of the major derivatives undergoes, a series of powders was prepared in which a derivative waa substituted for the normal content of centralite, and samples were heated. These powders were prepared on the same formula composition as RPL 142 and each contained one of the following compounds: centralite (control powder), N-nitroso-N-ethylaniline, N-nitroso-4-nitro-N-ethyIaniline, 4-nitrocentralite1 and 4,4'-dinitrocentralite. The conclusions which may be drawn from these experiments as well as from certain others are outlined in Figure 2. The control powder behaved in all respects as did RPL 142 and hence it may be assumed with some confidence that the reactions of the
H5C2.N,E-Ne
Q,
Figure 2.
C2H5
jb
Suggested Scheme for Formation of Identifed Derivatives
derivatives were normal. In that powder which contained Nnitroso-N-ethylaniline, the main derivative was N-nitroso-4nitro-N-ethylaniline, although the yield was far from quantitative. In the early stages of the heating some 2-nitro-Ar-ethylaniline was detected. The main product from N-nitroso-4-nitroN-ethylaniline was 2,4-dinitro-N-ethylaniline, although less than 20% of the reacted N-nitroso-4-nitro-Iethylaniline could be recovered in this form; some samples contained traces of 4nitroaniline. Both 4,4'-dinitrocentralite (main product) and .V-nitroso-4-nitro-N-ethylaniline were formed from 4-nitrocentralite, but N-nitroso-A'-ethylaniline could not be detected. Additional evidence that AT-nitroso-4-nitro-N-ethylaniline is formed from 4-nitrocentralite is to be found in Figure 1: The quantity of the compound increases during the decrease of 4nitrocentralite and after the exhaustion of N-nitroso-N-ethylaniline. A very small amount of trinitrocentralite was the only identified or unidentified compound which seemed t o be produced from dinitrocentralite. Most of the above reactions have involved the introduction of a nitro group into the molecule and it is reasonable to assume that this nitration occurs directly through the agency of some (unknown) product of decomposition of the powder or by nitroglycerin and/or nitrocellulose themselves. The formation of 2,4-dinitro-N-ethylaniline from iV-nitroso-4nitro-N-ethylaniline perhaps involves nitration followed by denitrosation in the manner which seems to be probable in the reactions of diphenylamine (84). No mention has yet been made of the nature of the reaction of centralite t o form N-nitroso-N-ethylaniline. LQcorchQand Jovinet (IS) state that N-nitroso-N-ethylaniline results from the nitrosation of the N-ethylaniline which arises from the hydrolysis of centralite as soon as the powder becomes acidic. This mechanism probably is inoperative in the stabilization of smokeless powder by centralite because centralite is much more resistant to hydrolysis by acid than would appear from their statements. They hydrolyzed centralite quantitatively in 3 hours by means of boiling 60% sulfuric acid at 150" C. Moisak (17) found that methylcentralite (1,3-dimethyl-1,3-diphenylurea)did not react with nitrous acid at room temperature during exposure for 6 months and reacted only slowly with nitric acid of a concen-
544
Vol. 42, No. 3
INDUSTRIAL AND ENGINEERING CHEMISTRY
tration less than 20%. During the present work, hydrolysis of centralite under still different conditions was attempted. A solution of 5 mg. of centralite per ml. of 5 11-hydrochloric acid in 1 to 1 ethyl alcohol-water (by volume) was refluxed for 113 hours. Two samples were taken during this period and one at the end, but no evidence of hydrolysis within the experimental error of the method, about 375, was obtained. Kone of these methods duplicates the conditions R hich exist in a smokeless powder, but the results indicate that drastic conditions and not meiely traces of acid are required for the hydrolysis of centralite. Consequently, the evidence is strong that A7-nitroso-hr-ethylaniline is formed by some direct action on the centralite rather than by hydrolysis and nitrosation; similarly, 1V-nitroso-4nitro-nT-ethylaniline may be formed by some direct action on 4nitrocentralite. Another type of reaction unquestionably occurs to some extent in centralite powders and it may give a clue to the reactions which produce the many unidentified minor pioducts. Although it is a minor reaction, de-ethylation is demonstrated by the detection of N-ethylcarbanilide and 4-nitroaniline. One might suppose that dephenylation would also be possible and there is some evidence for this if one assumes that the l-ethyl-3phenylurea, which was detected after destruction of the nitrocellulose with sodium peroxide, was iiot an artifact from the chemical manipulations on the nitrocellulose residue. Consequently, because such far-reaching and unusual reactions of centralite do occur in smokeless powder, it seems probable that the many minor derivatives are produced in the course of these or similar reactions. The reactions which produced such minor identified derivatives as 4-nitro-N-ethylaniline, 4-nitrophenol, and the like are obscure, although reasonable reactions might be proposed. It is indeed probable that the 4-nitro-itT-ethylaniline is an artifact which arises from N-nitroso-4-nitro-N-ethylaniline during the operations prior to chromatographic separations: Fresh extracts of the experimental powder v, hich contained N-nitroso-4-nitro-hethylaniline -rere free of 4-nitro-N-ethylaniline but older extracts contained it, especially if they had been exposed to light. In conclusion, then, there would appear to be three major reactions by which centralite is chemically changed in smokelesq ponder: (1)direct nitration by M hich, for example, 4-nitrocentrillite is formed from centralite and N-nitroso-4-nitro-S-ethylaniline from N-nitroso-A’-ethylaniline; (2) splitting of the molecule at normally reactive bonds by which appreciable amounts of A’nitroso-N-ethylaniline are produced from centralite or at relatively unreactive bonds by which small quantities of E-ethylcarbanilide are formed by de-ethylation; and (3) unknown reactions with nitrocellulose and/or nitroglycerin by which rather inextractable products are formed. Perhaps the third type of reaction is merely the major path of the second type, for in the process of splitting it may be that highly reactive fragments are formed which undergo ill-defined reactions. Further advance in understanding the reactions of centralite will lie in determining the nature of reactions of the third type. RELATION BETWEEN STATE OF STABILIZER AND CONDITIO\ O F POWDER
A previous discussion (24)has emphasized the fact that studies such as the present one are able to give at least a partial picture of the fate of a stabilizer in smokeless powder, but that they do not indicate what reactions the major constituents of the powder, the nitroglycerin and nitrocellulose, undergo, that they do not show the effect of the stabilizer on these reactions, and hence that conclusions about the ballistic usefulness and safe life of a powder cannot be determined from a knowledge of the state of the stabilizer. It is likewise inadvisable to draw conclusions about the merits of different stabilizers from studies such as these. Thus. in
double-base smokeless powder 0.7 % of diphenylamine is exhausted in 5 days a t 71’ C. (24), while the present study has shown that 1% of centralite a t 7 5 ” C. requires about 84 days. It might be concluded that diphenylamine is a poorer stabilizer because it is depleted so rapidly. On the other hand, it may also be argued that diphenylamine is effectively combining with deleterious products in the powder and that centralite is some what inert. Furthermore, the effectiveness not only of the original stabilizer itself but also of the derivatives must be considered. OPERATIONS ON SMOKELESS POWDERS PRIOR TO CHROMATOGRAPHY
Table I V gives the formula compositions, the granulations, and the method of manufacture of the cordite JP 76 and Radford pilot lot 142 of 1944 (RPL 142).
TABLE
Iv.
DATA FOR
76 AKD RPL 142 JP 76 49.62 (12.24) 41.41
Sitrocellulose, %
RPL 142 59. no
(13.22) (% Nitroglycerin, % ’ 40.00 8.98 1.00 Centralite, % Granulation Diameter of grain inches 1.7 0.8 Length of grain, i h h e s ” 1 2.5 Diameter of perforation, inch 0.6 0.25 Method of manufacture Solventless Solvent a Grains that are normally much longer were ciit to lengths indirated for convenience in heating.
Experimental powders, each of which contained a derivative in place of centralite, were based on the formula for RPL 142 but were manufactured by the slurry prdcess and were extruded in the form of 0.25-inch rod. The samples, each of which weighed about 45 grams, were stored in individual vented metal containers in electrically heated ovens a t 65’ * 2 ” C. or 75” =t2” C. Before chromatographic operations were carried out, centralite, its derivatives, and nitroglycerin a’ere separated from the nitrocellulose. This was accomplished by cutting the powders into slices 0.1 to 0.15 mm. in thickness by means of a slidingmicrotome and then extracting with anhydrous ether or methylene chloride for 2 to 3 hours in a Soxhlet aooaratus. Extracts in ether were first evaporated to remove t h y solvent, because i t is a strong eluent, and the residue was then taken up in benzene and diluted with an equal volume of ligroin; extracts in methylene chloride were either diluted directly with ligroin or concentrated somewhat and then diluted with ligroin. Because methylene chloride is comparable to benzene in eluting power, its presence in large proportion in solutions to be chromatographed is tolerable. MATERIALS
The adsorbent (a mixture of Merck reagent silicic acid and Celite 535 in the ratio 2 to 1by weight) and the solvents thxt were used have been discussed (24). Various streak reagents were used in order to detect the presence of colorless zones on the column: The “nitrous acid reagent” was a 1% solution of C.P. sodium nitrite in concentrated sulfuric acid; the “diphenylamine reagent” was a 1% solution of recrystallized diphenylamine in concentrated sulfuric acid; the “sodium hydroxide reagent” was a 6 N solution of O.P. sodium hydroxide; the “1-naphthylamine reagent” was a !% solution of 1-naphthylamiy in concentrated hydrochloric acid; the “ceric sulfate reagent, a 1%solution of “ceric sulfate” in 85% of sulfuric acid and 15% of water, was prepared by dissolving Ce(HSO& (G. Frederick Smith Chemical Company) in water and adding concentrated sulfuric acid, The ceric sulfate reagent when prepared in this manner deteriorates slowly; if 85% phosphoric acid is used in place of sulfuric acid, the reagent appears to b e stable. In order to aid in the identification of derivatives which were isolated chromatographically, many anticipated or possible derivatives were obtained commercially or prepared by unambiguous methods. The method of preparation, melting point, and some essential spectrophotometric properties of thosc dcriva-
INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1950 tives which actually were identified are presented in Table V. In addition to these compounds, many others were available f o r c o m p a r i s o n : These included tetranitrocentralite; nitroethylcarbanilidw; nitro, nitroso, and nitrosonitro d e r i v a t i v e s of aniline and N-ethylaniline; nitro derivatives of phenol; and various miscellaneous compounds. The spectrophotsmetric properties of all these compounds and the chromatographic properties of most of them were determined. APPARATUS AND METHODS
A description has been given elsewhere ($4) of the apparatus and the general chromatographic and spectrophotometric methods that were used. Because the extracts contained many unknown colorless compounds, the qualitative c h r o m a t o g r a p h i c work was carried out so that these compounds could be detected. By means of these methods, any substance which reacted with one or more of the streak rea g e n t s d e s c r i b e d above or which had a measurable spectrum in the visible or ultraviolet regions could have been detected.
TABLE v. METHODSOF PREPARATION, MELTINQPOINTS, AND CERTAIN SPECTROPHOTOMETRIC PROPERTIES OF CENTRALITE AND RELATEDCOMPOUNDS
Compound , Centralite
Citation for Method of Preparation” Commercial centralite recrvstallized from
ethylaniline 4,4’-DinitroObtained from R. L. centralite Shriner (I) 2,4,4’-TrinitroNitration of 4,4’-dinitrocentralite centralite N-Ethylcarbanilide (11) N-Nitroso-N-ethyl- (12) aniline N-Nitroso-4-nitro- Nitrosation of 4-nitro-NN-ethylaniline ethylaniline (7) 2-Nitro-N-ethylObtained from R. L. aniline Shriner 4-Nitro-N-ethyl(18, 26) aniline 2,4-Dinitro-Ar(is) ethylaniline 4-Nitro-N N(6,9) di?thydniline 4-Nitroaniline Eastman tech recr stal liliedfrom @OH &) 4-Nitrophenol Eastman WhiteLabelrecrystallized 6 N HCI
-
O
/I
N-C-R’,
147
147
None
161.5-152.3
91 91.0-91.5 B.p. 119.6-120 B.p. 150-154 a t 15 mm. a t 41 mm. 119-120 120.7-121.2
323-324
2.36
308-310
2.80
1.44
237-238 270-273
1.47 2.24
1.63 0.63
1.30
1.50
9-10
425
2.7
0.62
95-96
96.6-96.0
386-386
0.88
1.89
114
113.7-114.5
347
1.27
1.66
77-78
76.8-77.3
392-396
0.89
2.18
None
312-314
1.52
145-147
148
371-373
0.91
1.52
111.8-114
113.5-114.3
311-313
1.31
0.72
(8)
First reference is to method of preparation; melting points of oompound also given in other references. b Melting points within these extremes are stated in literature: values not necessarily those of any given preparation. C Calibrated thermometers were used and stem corrections were applied. d Other maxima were usually observed in speotrum but that given is convenient for spectrophotometric determination. e Units are in mg. per 100 ml. for 1 cm.; C = concn. in mg. per 100 ml.; D = log (Io/I) where D = optical density, Io = intensity of incident light, and I = intensity of transmitted light. These data and hence also E ?::, are probably accurate to .1;0.5% foroentralite and *2 or 3% for other compounds. / Molecular extinction coefficient. E?:: where c = conon. in moles per liter a n d 1 = length in om. = of solution traversed. 0 LBcorch6 and Jovinet (f5)described 4-nitrocentralite as difficultly crystallizable compound whioh forms orystalline complex with ethyl alcohol. Latter was observed, but 4-nitrocentralite itself did not crystallize.
The streak reagents ere useful in detecting compounds with certain substituents. Thus, the ceric sulfate reagent produces colors with a wide variety of compounds of the general structure
I
Melting point, 0 C. Lit. b Obsd.0 74-79 72.4
Spectrophotometric Data C/DS, Positiond mg./ Of Inax’ in loo abs. alo., for 1 E?&,’ mP em. X 10-4 247 3.07 0.873
a
The sample was placed on the column and developed with a volume of ligroin such that the total volume of sample solvent and developer did not exceed o,9 Vml, (t(Vml.jJ is the volume required to wet completely a column of adsorbent.) Consequently, even the most weakly adsorbed compound could not have been washed into the filtrate. Because ligroin is a weak developer, zones were generally detected a t the top of the Cohmn when it was streaked with various reagents. The lower section of the column which reacted with none of the reagents was eluted and the eluate was examined spectrophotometrically while the upper portion was eluted and the eluate Was prepared for rechromatography with stronger development. The process was repeated with stronger and stronger development until all evident zones had been isolated and all interzones had been studied spectrophotometrically.
R
545
in ~ ~ h i the c h nature of R and R’ may vary widely,
and accordingly was useful in the detection of derivatives which contained most of the structure of centralite. The l-naphthylamine reagent reacts with N-nitroso compounds. The diphenylamine reagent produces blue colors with nitrates and was useful in detecting nitroglycerin and the degradation products which were found. Sodium hydroxide forms colors with many nitro compounds.
identified by cornA derivative which had been isolated paring its color reactions, chromatographic behavior, and w e c i a b its absorption spectrum with those of the many compounds that were available. Although the spectrophotometric data of Table v are sufficient for the determination of an identified cornpound, they are not adequate for identification. However, even closely related substances of the types under d i m m h n have sufficiently unique spectra to make identification reasonably unambiguous when the entire spectral curve of an unknown compound agrees with that of a known compound. Some details of the chromatographic procedures for the isolation and roughly quantitative determination of centralite and of those of its derivatives which could be identified are given in Table
VI. DISCUSSION OF TABLE VI
In the following paragraphs are discussed certain factors that must be considered and certain precautions that must be taken in order to ensure satisfactory results by the methods outlined in Table VI. Because silicic acid may vary considerably in properties from lot to lot, changes in the volume of developer would probably be necessary before the chromatograms could be duplicated exactly. With the exception of the separation of 2- and 4-nitrocentra1itel each compound formed a well separated zone on that chromatogram from which it was eluted for spectrophotometric determination. All elutions were made with ether. The various compounds produce the following colors with a given streak reagent. With ceric sulfate reagent, centralite and
546
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLEVI. PROCEDURES FOR ISOLATION OF DERIVATIVES OF CEI~TRALITE FROU DOCBLEBASESMOKELESS POWDER Sample Solvent Developed Voll h t e r i a i to Be ume, Operation Chromatographed“?b Compn.% c mi. Compn.% c 1. Isolation of Use extract 2:lMC-1, 10 3kEinBt centralite (5 mg. of C) (4-nitro-C absent)5 2. Isolation of Mixture of C and 2: 1 B-L 5 1:4E-LI centralite (44-nitro-C BOnitro-C present) lated by 1 3. Isolation of Isolated as part of operation 2 4-nitro-C 4. Isolation of 4-Sitro-C zone iso- 2 : l B-I, 5 15% E A i n L/ 2-nitro-C latedin3 5 . Isolation of
4,4’-dinitro-C
6. Isolation of
N-nitrosoNETA
Mixture of 4-nitro-C and 4!4’dinitrp-C isolated by 1 Cse extract ( 2 mg. of compound)
2: 1 B-I, 1: 1 MC-L
5
10
Volume, mi. 2.5 NG
Remarkse washed into filtrate. C adsorbed in middle l / a of column
17
C present in lower column
3
2
2% E in L g , h
3
of
4-Nitro-C in top third of columnof 2 2-Nitro-C in lower 2/8 of coiumn immediately below 4-nit~o-C; not well separated 4,4’-Dinitro-C in middle pf column; 4-nitro-C in filtrate
4
1 : l E-Lg
2 / ~
Volatile compound. See discussion of ,Table VI. S G above X-nitroso\Il?rPd .UI11
7. Isolation of IT-nitroso-4nitro-NETA 8. Isolation of 4-nitro-NETA
Use extract (2 xng of compound) ~
1: 1 RIC-L
10
1: 1 B-1.g
L 2 5% E A i n L Isolated as part of operation 7
2 0.25 2
S G in filtrate 4-Nitro-SETA immediately above N-nitroso-4-nitro\.nm L
-\ E. 1 d
9. Isolation of
2-nitro-NETA 10. Isolation of 4-nitrophenol
Isolated as part of operation 6 a.
2-Nitro-NETA immediately beiow N-nitroso-NETA See discussion of Table VI
Use extract (1 1:l B-I, 10 1 : l B-LO 1.5 mg. of comL 0.5 pound) 12% EA in L 2 b. Material iso- 1:l B-L 5 8% A in LO 2 Compound in upper half of lated in 10a coiumn 11. Isolation of a. Use extract (1 1:1 B-L 10 1 : l B-Lg 2 Zone in middle third of colN-ethylcarbmg. of comL 0.5 umn. See discussion of anilide pound) 65” E A i n L 3 Table VI b. Material iso- 1: 1 B-L 10 3% A i n Lg 2 Zone In middle third of column iatedin I l a a B = benzene, L = ligroin (60-70’ C.), E = ether, A = acetone, EA = ethyl acetate, M C = methylene chloride C = centralite, NETA = AT-ethylaniline, S G = nitroglycerin. b Adsbrbent 2 to 1 silicic acid-Celite (either new o r reclaimed). Column dimensions, 19 X 200 mm., except: operation4 19 X 250 mm: operation6,25 X 150 mm. 0 Compositions given as katios by volume. d Unless otherwise specified, deveiopment was followed by poatwash of 1.5 V ml. of 303 t o 6 0 3 C. ligroin. V mi. is defined as volume of solvent required to wet column completely. e See discussion of Table VI for color reactions of comDounds. f Column prewashed with 0.2 V ml. of ether, V ml. of 1 to 1 acetone-ether, 0.8 V ml. of ether, and 2 V ml. of ligroin. IColumn preaashed with V mi. of ether and 2 Vml. of ligroin. h Column not postwashed.
2- and 4-nitrocentralite give a red color; dinitrocentralite, an orange (color develops slowly); and ll’-ethylcarbanilide, a purple. With I-naphthylamine reagent, AT-nitroso-N-ethylaniline and Ainitroso-4-nitro-AT-ethylaniline yield a pink color. With sodium hydroxide reagent, 4-nitrophenol forms a yellow color. The zones of 2- and 4-nitro-N-ethylaniline are yellow. When centralite and 4-nitrocentralite or 4-nitrocentralite and 4,4’-dinitrocentralite were present (centralite was exhausted before the appearance of the dinitro compound), the mixture was isolated by operation 1 and then separated by operation 2 or 5. In unheated powder, operation 1 was adequate for the isolation of centralite. The presence of emall amounts of 2-nitrocentralite does not interfere with the spectrophotometric determination of 4-nitrocentralite. n’-Nitroso-Ar-ethylaniline is so volatile a compound that special precautions were necessary to prevent losses. Extraction with methylene chloride was used in order to avoid evaporation before chromatography. After the chromatography and subsequent elution of the N-nitroso-N-ethylaniline R ith ether, 50 to 100 mg. of diethylene glycol were added to the eluate and the ether Tvas removed by evaporation under reduced pressure. During the evaporation, the temperature of the water bath was kept below 30”. The diethylene glycol diminished losses of Arnitroso-N-ethylaniline during evaporation but did not interfere with subsequent spectrophotometric determination. I n operation 10a the 4-nitrophenol is adsorbed between 4nitrocentralite (above) and centralite. If the section of the column between the middle of the zone of 4-nitrocentralite and the top of the zone of centralite is eluted and the eluate after
(8) (9) (10) (11) (12) (13)
(141 (15j (16)
(17) (18) (19) (20)
(21) (22) (23) (24)
(25) (26)
Vol. 42, No. 3 suitable manipulation is rechromatographed as in operation lab, 4-nitrophenol is more strongly adsorbed and easily separated from the contaniinants. S-Ethylcarbanilide also contains contaminants which may be removed by rechromatographing as in operation l l b . The recovery of the compounds in all the procedures is about 95%. ACKNOWLEDGMEN’I
It is a pleasure to ai,knodedge indebtedness to Robert B. Corey, under whose supervision this work m s carried out,, and to Linus Pauiing for his c o n t i n u e d i n t e r e s t a n d helpful suggestions. LITERATURE CITE[)
(1) Apard, A, MBm. p o i i d w s , 22, 180 (1926). (2) Ibid., 27, 11 (1937) (3) Beilstein, “ H a n d b u c h der o r g a n i s c h e n Chemie,” 4th ed., Vol. VI, p. 226, Supplement, p. 117, B e r l i n , J u l i u s Springer. (4) Ibid., Vol. X I I , p. 422. (5) Ibid., p. 711. (6) Ibid., p. 715. (7) Ibid., p . 728. Cook, S. G., IND. ENG.CHEM.,ANAL.ED.,7, 250 (1935’1. Davies, W.C., Bull. soc. chim., [5] 2, 295 (1935). Davis, T. L . , “Chemistry of Powder a n d Explosives,” P. 319, New Y o r k , John Wiley & Sons, 1943. G e b h a r d t , W., Ber., 17, 2093 (1884). Griess, P . , I b i d . , 7, 218 (1874). LBcorch6, H., a n d Jovinet, P. L . , Compt. rend., 187, 1147 (1928). L&corchB,H., a n d Jovinet,, P. L., 4Ie‘m.poudres, 23, 69 (1928). Ibid., p. 147. Masaki, K., B u l l . Chem. Soc. J a p u n , 7, 353 (1932). Moisak, I. J., Tram. KCrou. I n s t . Chem. Tech. Kazan, 1934, S o . 3, 133 (1935); Chem. Zentr., 107, I, 3620 (1936). Nolting. E., a n d Collin, A , , Ber., 17, 267 (1884). Norton, L. M., and Allen, -1. W., I3id., 18, 1995 (1885). Ovenston, T. C. J., a n d Parker, C. A, J . SOC.Chem. I d . (London), 66, 394 (1947). Parker, C. A . , J . Chem. Soc., 1946, 772. Parker, C. A , , J. Soc. Chem. Ind. (London),67, 434 (1946). S c h m i d t , O., Bel., 36, 2477 (1903). Fong. L. L., Trueblood, Schroeder, W,A, Malmberg, E. W,, K. N., Landerl, J. D., a n d Hoerger, E., IND.EKG.C H E ~ Z41, ., 2818 (1949). Smith, D. M . , B r y a n t , W. hl. D., a n d Mitchell, J., J . A m . Chem. SOC.,61, 2409 (1939). Weller, d.,Ber., 16, 31 (1883).
RECEIVED October 27, 1949. Contribution 1347 from the Gates and Crellin Laboratories of Chemistry. Based in part on work done for the Office of Scientifio Research and Development under Contract OEMsr-881 and in part on work done for the Navy Department, Bureau of Ordnance, under Contract NOrd-9652 with the California Institute of Technology. Linus Pauling was the official investigator. For the preceding paper, see ($4).
