INDUSTRIAL AND ENGINEERING CHEMISTRY
250
TABLEI. SOLUTIONS GIVINGPOSITIVE TESTS Iodide
Mg. 0.25 0.5 0.5 0.5 50.0 50.0
100.0 100 100 100 20
Bromide Mg. 0.25 0.5 2.5
100 0.5 0.5
100,o 100 100 1.0 0
ChIoride
Thiocyanate
Mg.
Mg. 100 100 100 100
0.25 0 0 0 0.5 0.5 15.0 0.25
however, they found it necessary to destroy the thiocyanate ion by ignition of the silver salts. The smallest quantity of bromide detected in mixtures was 5 mg. (page 161), which would make the method much less sensitive than that proposed by the authors.
50 0.5
100 100 250
100 0 0
0 100
The test for a bromide was much less sensitive in the absence of a thiocyanate. Less than 2 mg. of bromide ion could not be detected with certainty. If no bromide was present, the orange color due to the oxidation of the thiocyanate appeared but upon agitation disappeared in the course of about a minute. Since this work was done, Curtman and Schneiderman (1) have published a paper, which describes a method of detecting bromides in the presence of thiocyanates, using concentrated nitric acid to oxidize the bromide ion to bromine;
VOL. 7, NO. 4
Summary
A method of detecting halides in a mixture containing thiocyanates has been devised, by which as little as 0.25 mg. of iodide ion, 0.5 mg. of bromide ion, and 0.25 mg. of chloride ion can be detected in the presence of 100 mg. of thiocyanate ion. Literature Cited (1) C u r t m a n a n d Schneiderman, Rec. trav. chim., 54, 158-61 (1935). (2) C u r t m a n a n d Wikoff, J. Am. Chem. Soc., 37, 298 (1915). (3) McAlpine a n d Soule, “Qualitative Chemical Analysis,” p. 466, New York, D. Van N o s t r a n d Co., 1933. (4) Ibid., p. 572. (5) Sneed a n d D u s c h a k , J. Chem. Education, 8, 1388 (1931). R~CEIVE May D 13, 1936.
Determination of Diphenvlamine in Smokeless Powders STANLEY G. COOK, U. S. Naval Powder Factory, Indian Head, Md.
D
IPHEKYLAMINE is treat the p o w d e r w i t h about The purpose of this investigation was to a stabilizer introduced eight times its weight of concendevelop simpler and more accurate and trated nitric acid on the steam into smokeless powders practical methods for the determination of bath until the sample is all disfor the purpose of r e t a r d i n g diphenylaminein smokeless powders. solved, pour the solution into t h e i r decomposition. In old Four methods-nitration, soda distillawater, filter off the precipitated powders t h e r e i s c o n s i d e r nitro compound formed, dry, a b 1e 1o s s of diphenylamine, tion, extraction, and volumetric-are given cool, and weigh. The factors for some due to volatility of the in detail. All results are based upon analyconverting the weight of nitro diphenylamine as such, but more ses of prepared standard samples of known accounted for by nitration of c o m p o u n d to diphenylamine composition and verified by tests on manuv a r y f r o m 0.3981 to 0.4400, the diphenylamine by the defactured powders of known diphenylamine principally because of varying composition p r o d u c t s of the conditions which produce higher content nitrocellulose into n i t r o c o m or lower yields. pounds which have no value as Each method has its special application, The compounds formed by the stabilizers ( 5 ) . The need for depending on the age or condition of the nitration of pure diphenylamine a c c u r a t e methods to deterpowder to be tested. Excellent results were by concentrated nitric acid (sp. mine the a c t u a l a m o u n t of obtained with all methods. gr. 1.42) were found to vary conunchanged diphenylamine left siderably in comDosition as well in a Dowder a s w e l l a s t h e amouit which was originally added to the powder led to this as yield when equal weights of diphenylamink were nitrated investigation. Practically all of this author’s work is based with equal weights of nitric acid, and any variation in the following conditions made it impossible to produce the same upon Dreger’s (6) first efforts along this line, Much work weight of nitro compound: concentration of acid, duration has been done by others (1-13). Four methods for the determination of diphenylamine are of heating, temperature of heating, and quantity of water given: (1) the nitration method, which gives the total diused to precipitate the nitro compound. phenylamine originally added; (2) the soda distillation The use of fuming nitric acid improved the yield conmethod, which gives only the active or available diphenylsiderably but it was not until pure, dry nitrocellulose was introduced that much higher yields were obtained. It was amine left in the powder; (3) the extraction method, which gives both the active and the inactive diphenylamine; and (4) while working with reground powders in which the nitrothe volumetric method, which gives the active or available cellulose is very finely divided that difficulty was experienced. diphenylamine in new powders. Table I shows results found when treating 0.05 gram of pure diphenylamine with nitric acid and mixtures of nitric Nitration for Total Diphenylamine acid and glacial acetic acid, the nitric acid varying from 10 The literature on determining diphenylamine in smokeless to 100 per cent by volume and the acetic acid varying from 0 to 45 per cent by volume, no nitrocellulose present. All powder gives the well-known nitric acid method, which is to
.
JULY 15, 1935
ANALYTICAL EDITION
these results are below the weight of nitro compound produced by nitrating 5 grams of a 1 per cent diphenylamine powderwhich contained 0.05 gram of diphenylamine-with 10 cc. of glacial acetic and 20 cc. of concentrated nitric acid. TABLE I. RESULTSWITH NITRICA N D ACETICACIDS (No nitrocellulose, other conditions kept constant) Test
Glacial Acetic Acid
cc. 45 45 40 20 20 20 15 10 10 5
1 2 3 4 5 6 7 8 9 10 11 12
Concd. Nitric Acid Cc. 5 5
Nitric Acid (by volume)
% 10 10 20 20
10
5
10 10
331/3 331/3
15 20 20 25 20 20
0 0
50 662/3
662/3 83'/8 100 100
Nitro Compound Found Gram 0.0835 0,0822 0.0863 0.0863 0,0586 0.0837 0,0897 0,0949 0,0935 0.0920 0.0908 0.0908
Table I1 gives results with fuming nitric acid, all other conditions the same as in the above tests. 'rABLE
Sample 13 14 15 16
11. RESULTSWITH FUMING NITRICACID
Glacial Acetic Acid
Fuming Nitric Acid
cc.
cc .
10 10 10 10
Sulfuric Acid
%
Cc.
20
M2/3
20 10 20
W / a 331/3
.. ib
57.2
5
Nitro Compound Gram 0.1068 0,1080 0.1057 0.0987
Thefie results prove that to obtain high yields, oxides of nitrogen, which are produced by nitrocellulose, must be added to give a more highly nitrating power to convert the dipheqylamine completely over to hexanitrodiphenylamine, the final nitration product.
Diphenylamine Determination by Modified Nitric Acid Method
25 I
Per cent of diphenylamine = weight of nitro compound X 0.4259 X 100 weight of powder less total volatiles
METHODFOR ESTABLISHIKQ FACTOR. A weighed quantity of dry diphenylamine (0.05 gram) is transferred to a 250-cc. lipped beaker and 10 cc. of glacial acetic acid are added, stirred, and allowed to stand until all is in solution; 5 grams of dry nitrocellulose are then added and the acetic acid is mixed with nitrocellulose until it is as much colloided as this quantity of acetic acid will allow. Twenty cubic centimeters of nitric acid (sp. gr. 1.42) are added by washing down the sides of the beaker, so that all nitrocellulose will be in contact with the acid. The beaker is then covered with a watch glass and placed on the steam bath a t about 95" C. for 1.5 hours. The procedure from this point is identical with that when diphenylamine is determined in powder. EXPERIMENTS. A test of diphenylamine in a sample, No. 6, containing 2.65 per cent of total volatiles, was made, using various quantities of nitric acid and the factor corresponding to the particular quantity of nitric used, with all other details constant as above. Nitric acid, 00. Weight of nitro compound, gram Factor Diphenylamine, per cent
20 0,1100 0.1100 0.4259 0.96
30 0,1092 0.1097 0.4295 0.96
50 0.1072 0.1077 0.4333 0.956
A comparison of the straight nitric acid method without acetic using the same technic as to time, temperature, etc., and the same sample, No. 6, with 30 cc. of nitric acid, gave: Weight of nitro compounds, gram Av. Factor Diphenylamine, per cent Max. Min. Av.
0.1084,O. 1090,O. 1094,O.1097,O. 1107 0.1092 0.4295 0.977 0.956 0.963
Experiments indicate that the factor 0.4259 is sufficiently close to use with commercial diphenylamine containing 0.097 per cent of water:
Determining factors with pure diphenylamine and varying the amount of diphenylamine taken and quantities of acetic Five grams of powder, with total volatiles known, are weighed acid, nitric acid, and water used to precipitate, when the into a 250-cc. lipped beaker, 10 cc. of glacial acetic acid and 20 cc. of nitric acid (sp. gr. 1.42) are added, and the beaker is covered with a watch glass and placed on a steam bath at about 95" C. for 1.5 hours. The powder completely dissolves and diphenylamine :ISconverted to nitrodiohenvlamine. Red fumes are copiously evolved. ?'he 'time and temperature stated will allow all red fumes to be dissipated without too much reduction in volume and this is the end to be attained, as the nitro compounds have a tendency to crystallize out if the solution is evaporated too much or is allowed to stand t,oo long after removal from steam bath. Whenever such crystallization occurs results are slightly low. Immediately after the heating on'the steam bath is completed, the solution is cooled, being careful not to agitate it, and poured into 75 cc. of distilled water which has been cooled to 15" C. in a 250-cc. glass-stmoppered Erlenmeyer flask. The beaker is washed with water, so that the solution including washinp will be approximately 120 cc. The flask is shaken well for about 2 minutes and allowed to stand 2 hours. The nitro compound is filtered on a Gooch crucible prepared by washing with 10 per cent nitric acid and igniting. The nitro compound is washed 6 or 7 times with water containing 1per cent nitric FIGURE 1. APPARATUS FOR DETERMINATION OF DIPHENYLAMINE BY acid and dried a t 100" to 105" C. for 1hour. After DISTILLATION METHOD weighing, the Gooch is placed in a small beaker and 10 cc. of acetone are added and allowed to soak 15 minutes. The Gooch IS then placed in a suction flask time of heating and temperature ace kept constant, Table and washed with small quantities of acetone until nitro com111 gives a compilation o f results. promthe standpoint of pounds are completely washed out. The Gooch is dried at 100' speed, accuracy, and Practicability of method the mixture of to 105' C. for 1 hour and nitro compounds are determined by loss of weight. 2 parts of nitric acid and 1 part of glacial acetic acid proved The factor for conversion of nitro compounds to diphenylthe best. Where higher yields were obtained the time of amine, using the quantities of acid stated above, is 0.4259. solution was too long.
INDUSTRIAL AND ENGINEERING CHEMISTRY
252
The acetic acid modification is a distinct improvement in controlling the speed of reaction and allows closer checking on repeated tests than the straight nitric method, especially when reground powders are tested. The distinct increase in weight of nitro compounds, as the amount of nitric acid is reduced, may be due to solubility of the nitro compounds.
Nitration of Nitrodiphenylamines To determine, individually, the action of nitration on diphenylamine and the various nitrated products of diphenylamine, such as are produced in the natural aging of the powder, various weights of these compounds were taken, each weight being equivalent to 0.05 gram of diphenylamine, and the following were added : 5 grams of dry nitrocellulose, 10 cc. glacial acetic acid, and 20 cc. of concentrated nitric acid. This was run for 1.5 hours on the steam bath, and the determination carried out exactly as described above. The weight of nitro compound formed in each case was about 0.1160 gram. Using the factor of 0.4259 for converting to diphenylamine, the yields were almost 100 per cent, a very good indication that each one of these compounds nitrated to the same final nitration product-hexanitrodiphenylamine (Table IV).
(4) states that the compound's melting point is identical with the decomposition point which lies between 240' and 250' C. If the yield when nitrating diphenylamine were 100 per cent, the factor would be much lower, but the established factor of 0.4269 represents a yield of about 90 per cent. If all conditions of the test are kept constant there will be practically no change in this yield. Conversion Products of Diphenylamine in Powders In the slow decomposition of powder containing diphenylamine as a stabilizer, there are several steps in the breaking down of the diphenylamine which are considered to exist a t different ages of the powder. Beginning with the pure diphenylamine, the first step is the formation of diphenylnitrosamine, next nitrodiphenylnitrosamine, next dinitrodiphenylamine, and the final product is trinitrodiphenylamine ( 5 ) . The most generally accepted stages of conversion may be shown by the following formulas (9) :
(2) CsH5
CsH5'
TABLE111. DETERMISATION OF FACTOR NitroDiphenyl- cellu- Acetic Nitric amine lose Acid Water Acid Cc. Grams Cc. Cc. Gram 0.025 5 10 75 10 20 30
.,
50 0.05
5
10
75
0.05
5
75
0.075
5
15 20 10 10
0.075 0.10
5 6
10 10
ll! 75
125 75
10 20 30 20 20 20 10 20 30 .. 50 50 20 30
Nitro Compound Gram 0.0633,0.0643,. . . . 0.0611,0.0611,0.0610 0.0605,0.0600,0.0605 0,0603,O. 0605, . . . . 0.0601.0.0590.0.0593 0.1200,0.1200,0.1210 0.1174,0.1175,0.1174 0.1170,O.1161,O.1160 0.1186,0.1184, , . . . 0.1167,O.1178, . . . 0.1183.0.1185.0.1177 0.1760,0.1780,. . . . 0.1747,O. 1744, . . . 0.1746,O.1747,O.1746 0.1749,O.1746,O.1747 0.1695,O.1690, . . . 0.1676,0.1678, . . . . 0.2319,O 2314,0.2322 0.2293,0.2274,0.2276
.
.
.
Factor AV.
0.3920 0.4091 0.4145
....
0.4181 0.4149 0.4259 0.4297 0.4219 0.4266 0.4229 0.4237 0.4293
....
0.4293 0.4430 0.4472 0.4314 0.4385
TABLEIV. NITRATION OF DIPHENYLAMINE AND ITS NITRATED PRODUCTS (Using 5 grams of dry nitrocellulose with 10 cc. of glacial acetic acid and 20 cc. of concentrated nitric acid 1.5 hours on steam bath) Nitro Yield as Actual Equivalent Compounds Taken Weight Diphenyl- Compound Diphenylamine Found aminea for Nitration Taken Diphenylamine, m. 52.5' C.
p.
Gram
Gram
Gram
%
0.0500
0.05
0.1169 0.1176
99.57 100.00
Diphenylnitrosamine, m. p. 66.0' C. 0.0585 Nitrodiphenylnitrosamine, 0.0719 m. p. 130' C. Dinitrodiphenylamine, m. p. 0.0766 156.5' C. Trinitrodiphenylamine, 0.0930 m. p. 181.b' C. a Facto: 0.4259 used for conversion.
0.05
0.1159
98.72
0.05
0.1168
99.49
0.05
0.1157
98.55
0.05
0.1150
98.20
To verify this by melting point, small amoun+,s of the yellow nitro compound were placed on the surface of mercury contained in a large porcelain crucible in which was supported a thermometer. Melting points gave 239" to 242' C. Beilstein (1) and Marshall (11) give 238" C. as the melting point for 2, 4, 6, 2', 4',8'-hexanitrodiphenylamine, the symmetrical form. When using a regular melting point tube for the test, the compound seems to decompose slowly and reading is impossible. According to International Critical Tables ( 8 ) , hexanitrodiphenylamine decomposes a t 250' C. Colver
VOL. 7, NO. 4
(3)
\N-N
=
o
NOz
Nitrodiphenylnitrosamine
Molecular weight, 243.0 Melting point, 130.0' C.
,N-N=O C6Ha
(4) c6H4SN0' N -H
(4,4') (2,40
Dinitrodiphenylamine Molecular weight, 259.0 Melting point, 156.5' C.
(2,4140
Trinitrodiphenylamine Molecular weight, 304.0 Melting point, 181' C.
C6H4\ NOz ~(N0z)r (5) c ~ H a \--H ~ c6H4(
Diphenylamine Molecular weight, 169.1 Melting point, 52.5" C. Diphenylnitrosamine Molecular weight, 198.10 Melting point, 66.0" C.
(2,4,2') NO2
Table IV proves that if, in the natural aging of the powder, there were present any one of these nitrodiphenylamines, the results by the nitration method would include both the diphenylamine as such and the combined diphenylamines. I n most powders the nitration method gives accurately the amount of diphenylamine, but in old or reworked powders it gives only the total diphenylamine added and fails to show the amount of available or active diphenylamine left. The active diphenylamine includes both diphenylamine and diphenylnitrosamine. Therefore, other methods were developed for determining active diphenylamine and are described below.
Soda Distillation for Active Diphenylamine The development of the soda distillation method for determining active diphenylamine in smokeless powder is based upon Dreger's method (6) of dissolving the powder in sodium hydroxide solution and distilling with steam with subsequent bromination of the ether extract. Various modifications of this method were tried: (1) varying percentage of sodium hydroxide solution from 5 to 40, (2) varying amount of solution used, (3) varying time of distillation, (4) varying speed of distillation, (5) varying amount of bromine used, (6) using ether instead of alcohol, (7) using acetic acid as bromination medium, and (8) varying size of flasks, length of condenser, etc. Inasmuch as only diphenylamine and diphenylnitrosamine are valuable as stabilizers, it was necessary to verify the bromination method t o see if these two compounds could be separated from the powder together and determined ac-
JULY 15, 1935
ANALYTICAL EDITION
RESULTSON DIPHENYLAMINE TAIILE v. BROMINATION IN ETHERSOLUTION Theoretical weight of Bromine -Bromine Diphenyl- Necessary t o amine Brominate Gram 0.015
Gram 0.057
Gram 0.64
Added% Excess by weight
%
Cc.
0.20
Diphenylamine (basis 5 g. powder) Added Found
1000.0
%
0.30
0.30 0.31 0.025 0.10 0.64 0.20 540.0 0.50 0.51 0.50 0.49 0.050 0.19 0.64 0.20 237.0 1.00 1.01 1.02 0.075 0.29 0.64 0.20 120.0 1.50 1.51 1.52 0.100 0.38 0.64 0.20 70.0 2.00 1.98 0.050n 0.19 0.64 0.20 237.0 1.00 1.00 0.050'' 0.19 0.64 0.20 237.0 1.00 1.00 a 0.1 gram of nitrocellulose was added t o these samples and then after evaporation 10 grams of sodium hydroxide in 100 cc. of water were added to dissolve the nitrocellulose.
TABLEVI. RESULTSON POWDERS Sample
Total Volatiles
% 6 16 8
13
3.45 2.65 4.55 4.55
Diphenylamine Added to Powder
% 1.00 1.00 1.00
1.00
Diphenylamine Found
% 0.96,0.95 0.97,0.97 1.04,1.04 0.98, 1.00
TABLE'VTI. BROMINATION OF DIPHEKYLAMINE AND ITS NITRO COMPOUNDS BY BROMINE IN ETHEREXTRACT (After distilling with steam and 10 per cent sodium hydroxide) DiphenylBromo Compound amine Compound Diphenylamine Compounds Used Taken Equivalent Found Yieldo Foundb Gram Gram Gram % % Diphenylamine O.OSO0 0.05 0.1435 100 1.00 Diphenylnitrosamine 0,0585 0.05 0,1444 100 1.00 Nitrodiplienylnitrosamine 0.0719 0.05 0.0035 2.4 0.02 Dinitsodiphewlamine 0.0766 0.05 0.0020 1.4 0.01 Trinitrodiphenylamine 0.0930 0.05 0,0000 0 0 a Factor 0.3487 used for conversion. b On basis of 5 grams powder.
253
PROCEDURE. (1) Distillation of powder with steam in sodium hydroxide solution, (2) extraction of distillate with ether, (3) bromination of diphenylamine and evaporation with air, and (4) boiling with 5 per cent sodium hydroxide t o break up lumpy tetrabromodiphenylamine. Exactly 5 grams of sliced powder (total volatiles known) are weighed, transferred to a 500-cc. Ladenburg flask and 200 cc. of 10 per cent sodium hydroxide solution are added. The flask is supported on an electric heater set a t 1 ampere (Central Scientific Co. No. 533 asbestos top with 6.25 cm., 2.5 inch, diameter opening). The side arm of Ladenburg flask is connected to a 50-em. (20-inch) water condenser, at other end of which is an ada ter leading into a 1000-cc. separatory funnel to catch the distilEte. Steam is passed into the Ladenburg flask by means of a glass tube, one end of which reaches to the bottom of the soda solution in the flask, the other end going through a Kjeldahl connecting bulb into a 1-liter flask containing water and set on an electric flask heater (Fisher Scientific Co., Type H, 550 watts). Steam distillation is continued until 500 cc. collect in the receiver, then the apparatus is disconnected and allowed to cool. The condenser and adapter tube are washed out with about 85 cc. of ether into the separatory funnel, 10 grams of sodium chloride are added, the funnel is shaken well, and allowed to stand until water layer is clear. The water layer is drawn off and the ether layer caught in a dry 250-cc. beaker. The extraction is repeated with another 85 cc. of ether. To the combined ether extracts 0.2 cc. of pure bromine is added carefully, all ether and bromine are evaporated off on low-temperature bath at about 75' C. with air, 100 cc. of 5 per cent sodium hydroxide are added, boiled 2 minutes, filtered on a weighed Gooch crucible, and washed well with hot water. The crucible is dried in oven 1 hour a t 105' C., cooled, and weighed. The precipitate is tetrabromodiphenylamine. weight of ppt. X 0.3487 X 100 Per cent of active diphenylamine = weight of powder less total volatiles
The powders in Table VI are all new and show no loss of diphenylamine. Diphenylamine and diphenylnitrosamine distill over with steam 100 per cent. Each test in Table VI1 represents the bromination of 0.05 gram of diphenylamine or its equivalent weight of nitro compound. For example, 0.093 gram of trinitrodiphenylamine represents the weight of this substance which would be formed TABLEVIII. BROMIXATION OF NITROCOMPOUNDS OF DIPHENYLAMINE WITH BROMINE IN in 5 grams of a 1 per cent diETHERAND GLACIAL ACETICACID Molecular phenylamine powder, providing Weight of Melting Point of the powder has aged t o such a n Compounds Used for Weight Weight Color of Compound Compound Compound Bromination Taken Found Found Taken Taken Found extent that all Of the diphenylGram Gram o c, o c, amine had changed over to this Bromination in Ether form. Nitrodiphenylnitroaamine 0,0719 0,0910 Dark brown 243 131 112 According to previous investi0.0719 0.0930 gators ( 5 ) ,no nitro compounds of 0.0719 0.0937 Dinitrodiphenylamine 0.0766 0.1000 Orange 259 157 138 diphenylamine beyond the stage 0.0706 0.1044 Trinitrodiphenylamine 0.0930 0.0920 Golden, same as of t h e trinitrodiphenylamine 0.0930 0.0890 original 304 lg8 lS7 have ever been found in old Bromination in Glacial Acetic Acid Nitrodiphenylnitrosamine 0.0719 0.1354 Bright yellow 243 131 205 powders, so in this investigation Dinitrodiphenylamine 0.0766 0.1113 Orange and dark it was not necessary to try the brown mixed 259 157 142 Trinitrodiphenylrtmine 0.0930 0.0970 Yellow or golden 304 188 185 effect of the tetranitro or higher nitrated diphenylamines when treated with bromine. curately. As in the nitric acid method, standards were In the case of the distillation and bromination of nitrodirun by taking known weights of pure diphenylamine (0.05 phenylnitrosamine and dinitrodiphenylamine, a small weight gram in each case) and running them through after adding 5 of residue (0.0035 and 0.0020 gram, respectively) was found. grams of dry nitrocellulose, Calculating this to a basis of diphenylamine in 5 grams of Results when following the Dreger method were not satissample gives results of 0.02 and 0.01 per cent of diphenylfactory, so ether was used instead of an alcohol medium in amine. It is unlikely that at any time during the natural which to brominate. Too large a sample is required in the aging of a powder all the diphenylamine would be converted Dreger method as well as too long a time for distillation. to either nitrodiphenylnitrosamine or dinitrodiphenylamine Table TJ shows clearly that excellent results were obtained and therefore this small percentage would not vitiate the with ether, and that 0.2 cc. of bromine is ample for powders results sufficiently to justify discarding the method or making containing as high as 2 per cent of diphenylamine. a correction for that amount. After determining the safe amount of bromine necessary T o determine the effect of brominating the three nitrodiand the best solvent, actual tests were made on samples of phenylamines in ether and acetic acid, known weights of powder containing 1per cent of diphenylamine. these compounds were dissolved in these solvents and 0.2 cc.
-
254
INDUSTRIAL AND ENGINEERING CHEMISTRY
of bromine was added. Three other tests were made by the regular volumetric bromination method, using alcohol as a medium, with potassium bromate-bromide solution. The first two compounds are brominated to some extent but the trinitrodiphenylamine is not. In the volumetric tests no definite end point could be obtained in the case of nitrodiphenylnitrosamine and only a small titration of 2.6 cc. of sodium thiosulfate, equivalent to 0.005 gram of diphenylamine, was found in the case of dinitrodiphenylamine. These results throw out the direct bromination of powder after extraction when the powders contain any nitrodiphenylnitrosamine or dinitrodiphenylamine. On new powders direct bromination of the ether extraction will give accurate amounts of diphenylamine in the powder. Table VI11 clearly establishes the fact that the direct bromination of the ether extract of any powder which contains nitrated diphenylamines beyond the diphenylnitrosamine stage is not an accurate method for determining the total diphenylamine or the unchanged or active diphenylamine.
TABLEIX. RESULTSOF BROMINATION OF DIPHENYLAMINE BY VOLUMETRIC METHOD Diphenylamine b Added Found Known standard" Sample 14 Sample 66
Five grams of powder, total volatiles known, are weighed into a conical 100-cc. weighing bottle. Powder may be in whole grains if small size or in slices as needed for a fair sample. Fifty cubic centimeters of ether, prepared by washing with water and distilling are added and sample is placed in ice box for 24 hours; then 0.5 to 1 cc. of alcohol is added and let stand 24 hours more. This treatment will soften and swell the powder so that extraction is easy without having the powder break up. Some samples may require slightly more alcohol, but it is better to give more time soaking. When soft, the sample is transferred to a 30 X 80 mm. paper thimble in Soxhlet extractor using a long-tube aluminum funnel with tube wide enough to allow powder to fall through freely; the powder is washed into the thimble with ether until the extractor flask, holding 250 cc., is half full. The powder is extracted 6 hours on a water bath and extract t,ransferred to a 200-cc. long-neck side-outlet distilling flask, using 25 cc. of water, and distilled with steam using the same condensing and heating arrangements as in previous method. The ether is first carefully distilled at low heat and finally the water in the distilling flask is heated and steam passed through until ether and water collected are about 400 cc. The distillate is extracted and brominated exactly as in the previously described method. The residue in the distilling flask contains all nitro compounds above the diphenylnitrosamine. The contents of the distilling flask are transferred to a 250-cc. beaker and evaporated to dryness. The dried flask is washed out with glacial acetic acid to dissolve nitro compounds, heating on steam bath as necessary. Just 10 cc. of total acetic must be used for this. The washings are poured into the beaker containing the dried residue from the distilling flask; the flask is then washed out with two 10-cc. portions of nitric acid (sp. gr. 1.42) and these washings are added to the acetic acid washings with 3 grams of air-dry nitrocellulose. The nitro compounds are determined from this point by the regular nitric acid method. The product is hexanitrodiphenylamine,
%
%
1.00 1.00 1.00 0.99 0.99 0.99 0.99 0.99
1.00 0.99 0.99 0.99 0.99 0.99 0.96 0.96
Sample 6 Sample 1614 a 0.05 gram of diphenylamine, 0.60 gram of plasticizer a , 0.25 cc. of plasticizer b , 0.10 grams of nitrocellulose, and 25 cc. of ether. b Basis of 5 grams of powder.
TABLEX . BROMINATION OF THREE NITRODIPHENYLALCOHOLBY MEANSOF POTASSIUM BROMATEBROMIDESOLVTION
AMINES IN
Extraction Method Old powders which were thought t o contain some nitrodiphenylamines were run by the distillation method. The residue in the flask which also contained some sodium hydroxide, water, and the saponification products of the powder, was taken to dryness in a beaker, neutralized with nitric acid, and carried from hereon by the regular nitric acid method. The large amount of salts present interfered with this test. Extraction of the nitro compounds with ether also proved unsuccessful. Softening of the powder with ether was tried with subsequent extraction in Soxhlet extraction apparatus, and found to be successful. PROCEDURE. (1) Soften powder with ether and little alcohol, (2) extract with ether in Soxhlet with thimble, (3) distill extract with steam, (4) extract distillate with ether and brominate, and ( 5 ) evaporate residue in distilling flask and nitrate residue in glacial acetic acid.
VOL. 7, NO. 4
Weight Taken Gram
Sodium Thiosulfate Used
Ni trodiphenylnitroeamine
0.0719
cc . ..
Dinitrodiphenylamine Trinitrodiphenylamine
0.0766 0.0930
Nil
Diphenylamine Gram No definite end point 0.005
2.6
Nil
TABLE XI. TESTSON POWDERS BY VOLUMETRIC METHOD Method
Diphenylamine
70 Sample 8, newly made powder 0.98, 1 . 0 0 Volumetric Nitric acid 0.99 Soda distillation 0.99 Special powder No. 1 with plasticizers, a new powder 0.97 Volumetric Soda distillation 0.98 Extraction 0.98
for which the factor to convert t o equivalent diphenylamine is 0.4259. When powders are new this method may be so far modified as to omit arts 3, 4, and 5 of procedure arid brominate directly in the etier which has been used to extract the powder in part 2.
Specially Prepared Powders Containing Certain Plasticizers The nitration method has been found inapplicable to powders containing certain plasticizers, but the soda distillation, extraction, and volumetric methods give good results when slightly modified as follows: SODADISTILLATION METHODFOR SPECIALPOWDERS. The distillation is carried out with 20 per cent sodium hydroxidewater solution with extraction and bromination as heretofore described to the point where ether is evaporated from the bromo compound; when the bromo compound is dry, 40 cc. of 95 per cent ethyl alcohol are added and the mixture is brought to the boiling point. Forty cubic centimeters of water are t8henadded and the beaker is left on the steam bath for 10 minutes. The bromo compound is filtered warm on a Gooch crucible and washed with 80 cc. of warm 47.5 per cent ethyl alcohol (by volume) and finally with hot water. Drying and weighing of the tetra-bromo compound are as for nitrocellulose powder. Diphenylamine in these powders is reported on the basis of powder with moisture and volatile solvent. Per cent of
= weight of bromo compound X 0.3487 X 100
weight of powder
The powder is EXTRACTION METHOD FOR SPECIAL POWDERS. softened and extracted with ether as for straight nitrocellulose powder; the extract is transferred to a 250-cc. beaker, bromi-
JULY 15, 1935
ANALYTICAL EDITION
=
TABLEXII. COMPARISON OF RESULTS Diphenylamine Found (corrected for volatiles)
Method
% A. Soda distillation B . Extraction with ether, then separation with steam and bromination C . Extraction with ether, then direct bromination D. Same as C except using volumetric method E. Residue in flask from B by nitric wid method F. Total dipheny!amine by nitric acid method Total diphenylamine by F lees amount by A = converhed diphenylamine
0.38 active 0.36 active 0.64 0 30 0.46 inactive 0 85 0 47 inactive
TABLEXIII. COMPARISON OF RESULTS ON REWORKED POWDERS (Results on four 5-gram samples of reworked powders using the nitric acid, distillation, and extraction methods) Diphenylamine Found (corrected) Method 1 2 3 4
255
nitrocellulose are added, the ether is evaporated with air, and 50 cc. of ethyl alcohol are added to each. Twenty cubic centimeters of standard 0.2 N potassium bromate-bromide solution are added, the flasks cooled in ice water, 10 cc. of concentrated hydrochloric acid added, and the flask is placed in ice water for 2 minutes. Ten cubic centimeters of 10 per cent potassium iodide are added and after 3 minutes the mixture is titrated with 0.1 N sodium thiosulfate, using starch as indicator. A B
= cc. used for blank = cc. used in titration
= 38.7 = 14.2
__
C = cc. necessary 24.5 N = normality of sodium thiosulfate = 0,0985 FV = weight of sample taken = 5 grams 1 cc. of N sodium thiosulfate = 0.021136 gram of diphenylamine B ) N X 0.021136 X 100 Per cent of diphenylamine = ( A in powder W = (38.7 - 14.2)0.0985 X 0.021136 X 100 = l,ol 5
-
With the diphenylnitrosamine it was difficult to get an end point. A fair end point was finally reached, but when calculated it amounted to a small titration of only 4.3 cc., % % % % whereas the titration should have been 23.85 cc. as with the 0.54 0.54 0.54 0.52 Nitric acid former test. Calculating this titration gives a weight of 0.49 0.46 0.46 0.45 Soda distillation 0.50 0.46 0.46 0.45 0.009 gram of diphenylamine found or 0.18 per cent in the .. 0.47 .. 0.51 powder, which is a yield of only 18 per cent of diphenylamine. Av. 0.50 0.46 0.46 0.45 If diphenylnitrosamine is present in the extracted popder, Extraction with ether, then separation 0.45 0.48 0.45 with steam and bromination 0.49 only a small proportion of it will be titrated. I n the first 0.50 0.45 0.45 0.45 place, a good end point is difficult to arrive at, perhaps on acAv. 0.50 0.45 0.47 0.45 count of a liberation of nitrous oxides during the reaction. Residue in flask from extraction by nitric acid method 0.05 0.10 0.04 0.05 If an unknown sample of powder happened to contain this - - - nitrosamine, the volumetric bromination method would be Sum ,of active and inactive diphenylamine 0.55 0.55 0.51 0.50 inaccurate but, on new or fairly new powders, this method is acceptable for straight nitrocellulose powders and specially TABLEXIV. COMPARISON OF RESULTS ON NEW POWDERS prepared powders containing plasticizers. (Table X.) As far as the investigation has gone, the volumetric method Diphenylamine Found Powder Soda distillation Extraction method gives good results even in old powders, providing they do not Analyst 1 Analyst 2 Saimple Analyst 1 Analyst 2 contain any diphenylnitrosamines. (Table XI.) :rs
1 !il 6
%
%
%
%
1.04 0.98 0.94
1.04 0.98 0.95 0.96
1.06 0.98 0.97 0.97
1.03 0.98
..
0:9s
nated, and the bromo compound dried as for straight nitrocellulose powder. Forty cubic centimeters of 95 per cent ethyl alcohol are then added, the liquid is brought to the boiling point, 40 cc. of water are added, and the beaker is left on the steam bath for 10 minutes. The liquid is filtered on a Gooch crucible and washed with 80 cc. of warm 47.5 per cent ethyl alcohol (by volume), driedL1 hour at 105” C., cooled, and weighed. The crucible is washed with hot benzene, dried, and reweighed; the difference in weight is bromo compound. Per c,snt of
= weight of bromo compound X 0.3487 X 100
weight of powder
The warm alcohol solution dissolves all plasticizer compounds but not the tetrabromodiphenylamine. The hot benzene dissolves the tetrabromodiphenylamine but none of the nitrocellulose ,which comes through during the extraction of the powder in Soxhlet apparatus. VOLUMETRICMETHOD FOR SPECIAL POWDERS. This method is identical with the volumetric method for straight nitrocellulose powders, described below. Table IX gives results of tests of bromination of diphenylamine by the volumetric method in ethyl alcohol in the presence of certain plasticizers and nitrocellulose and in specially prepared powders containing these plasticizers. The presence of plasticizers does not interfere in any way with the bromination of the diphenylamine.
’Volumetric Method for Smokeless Powders This method (3) was verified for accuracy by using known amounts of materials. In two separate flasks 0.05 gram of diphenylamine and 0.0585 gram. of diphenylnitrosamine are dissolved in ether, 5 grams of
Comparison of Results by Four Methods Sample 6 was heated for 350 days a t a temperature of 65.5” C. This heating caused the powder to age very fast and Table XI1 shows results determined by all the methods described in this paper. Total volatiles equaled 0.98 per cent. I n the case of D, the end point was difficult to determine, and thus the result is not reliable. Test C gave 0.64 per cent diphenylamine. This confirms previous tests that total diphenylamine in an old powder cannot be found by extraction of the powder with subsequent bromination. The other tests check very well. The sum of A , active diphenylamine, and E , inactive diphenylamine-O.38% 0.46% = 0.84%checks F , 0.85 per cent total of active and inactive diphenylamine in the powder.
+
Literature Cited (1) Beilstein, “ H a n d b u c h der Organischen Chemie,” 4th ed., Vol. X I I , p. 766, Berlin, Julius Springer. (2) Bresser, A,, Z . ges. Schiess-Sprengstoffw.,30, 42-3 (1935). (3) Buisson, “Problbme des Poudres,” p. 127. (4) Colver, “High Explosives,” p. 361, N e w York, D. V a n Nostrand
Co., 1918.
(5) Davis, T. L., a n d Ashdown, A. A., IND.ENG.CHEM.,17, 674 (1925). (6) Dreger, W., Z . ges. Schiess-Sprengstoffw., 1909 (4), 123. (7) Ellington, 0. C . , a n d Beard H. G., J. Soc. Chem. Ind., 50, 151T (1931). (8) International Critical Tables, Vol. I, p. 244, N e w York, M c G r a w Hill B o o k Co. (9) Juillard, P., Bull. soc. chim., 33, 1172 (1905). (10) Marahall. “Exdosives.” 2 n d ed., Vol. 2, R . 672. Philadelphia, P. Blakiston’s Son & Co., 1917. (11) Ibid.. Vol. 3. D.233. t12j R y a n , H., Keane, J., a n d Dunne, J., Sci. Proc. Roy. Dublin Soc., [N. S.]19,85-100 (1928). (13) T u r e k , O., Chemicky Obzor, 1, 295-8, Chem. Zentr., 1927, 11, 999. RECEIVED March 8, 1935.
