Table
the nitrometer values may be slightly lower and the transnitration ones slightly higher than theoretical. For the nitrometer, transnitration, and titanium(II1) chloride methods, operator and lot variability are probably of greater significance than differences in precision of the three methods.
II. Data for Methods Yielding Total Nitrogen Kjeldahl
Lot HC-5366 1458 Eastman 77 78A Av. of 5 lots Table 111.
Mean 53 42 53 39 53 00 52 94 53 38 53 23
Dumas Std. dev. 0 15 0 0 0 0 0
Mean 53 92 54 07 53 41 53 93 54 03 53 87
18
12 22 17 17
Std. dev. 0 17 0 04 0 33 0 14 0 17 0 17
LITERATURE CITED
Per Cent Nitroguanidine by Various Methods
NiTransLot trometer nitration HC-5366 99.78 100.15 99.78 100.22 99.70 100.52 100.30 1458 99.70 100 45 99.78 100 45 99. 70 Eastman 99.48 99.48 99,85 99.63 99.55 99.55 77 99.70 100.00 100.15 99.63 99.63 99.93 78.4 99.70 100.45 100.07 99. 70 99.63 100.52 100,14 Av. of 5 lots 99.67
The Kjeldahl consistently values. Transnitration trends to centages higher than the value. The nitrometer method
BowmanScott 98.81 100.07 99.55 98.74 99 18 9 i 85 100 22 99 55 99 70 100 45 100 45 99 26 99 78 99 93 100 00 99 57
yields low give pertheoretical gives the
Titanium(111) Chloride Kjeldahl 99.33 99.50 99 20 99.70 100.00 98.96 99.85 99.37 99 93 99 35 99 85 98 79 100 30 98 66 100 30 98 46 100 22 98 24 99 26 98 79 99 18 98 09 98 09 99 55 99 41 99 85 99 93 99 26 98 79 99 93 99 81 98 86
Dumas 100.35 100.32 99.80 100.43 100.37 100.50 99.67 98.51 99.41 100.00 99.93 100.45 100.35 100.04 100.65 100.05
R. W:,Shaefer, W. E., in “Organic Analysis,” 5’01. 11, pp. 71122, Interscience, S e w York, 1954. (2) Bovman, F. C., Scott, IT. IT., Znd. Eng. Chem. 7,766 (1915). (3) Brandt, W. TT., DeVries, J. E., Gantz, E. St. C., ASAL. CHEX 27, 392 (1955). (4) Davis, Tenny L., “Chemistry of Powder and Explosives,” pp. 384-5, Kiley, Sen- York, 1943. (5) Kolthoff, I. bl., Robinson, C., Rec. trav. chzrn. 45, 169 (1926). (6) Siederl, J. B., Siederl, V., “Micromffthods of Quantitative Organic Analysis,” 2nd ed., pp. 79-99, Kiley, S e w York, 1942. (7) “Scott’s Standard Methods of Chemical iinalysis,” N. H. Furman, ed., 5th ed., pp. 632-3, Van Nostrand, New York. 1939. (8) Ibid., pp. 649-52. (9) Stalcup, H., Williams, R. JV., AXAL. CHEW27,543 (1955). (10) Sternglanz, P. D., Thompson, R. C., Savell, W,L., Ibid., 25, (1953). (11) Wegman, R. F., Roth, Milton, Picatinny Arsenal Tech. Rept. 2428, July 1957. (12) Zimmerman, R. P., Lieber, E., .4NAL. CHEN. 22, 1151 (1950). (1) Becker,
Av. of 6 Methods 99.76 99.70 99.49 99 .59 99 .89
greatest precision, but if the compound is assumed pure, the results are slightly less than the theoretical value. For the assay of total nitrogen the Dumas is to be preferred. For the assay of KOz-group nitrogen,
RECEIVEDfor review January 8, 1958. Accepted May 10, 1958. Division of Analytical Chemistry, 133rd Meeting, ACS, San Francisco, Calif., April 1958.
Reaction of Nitrates and Nitramines with Phosphoric Acid C. L. WHITMAN and MAE I. FAUTH Research and Development Department, ,Examination of the behavior of phosphoric acid as a reagent in the nitrometer reaction showed that, although inorganic nitrates reacted quantitatively, nitrate esters and nitramines were not soluble or the reaction was incomplete. A modification of the diphenylamine spot test for nitrates was found to differentiate nitrates, nitrites, and nitrate esters, from nitramines. All these classes of compounds gave positive results when a test reagent consisting of diphenylamine in sulfuric acid was used. When the diphenylamine was dissolved in phosphoric acid, nitramines failed to give the test. This difference in behavior permitted the detection of nitrates and nitrate esters in nitramines.
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ANALYTICAL CHEMISTRY
U. S.
Naval Powder Factory, Indian Head,
A
Md.
SUMMARY of
the methods of analysis for nitrates and similar compounds, together with extensive references, has been given by Becker and Shaefer (1). The use of diphenylamine in sulfuric acid as a spot test reagent for nitrates and nitrites mas described by Feigl ( 3 ) . Kieland (4)studied the reaction of diphenylamine with nitric and nitrous acids and proposed the following set of equations:
H I
W
-
D
HNOs T HKOz
Diphenylamine (colorless)
S,S’-Diphenylbenzidine
(colorless)
--
HSOI or HSOs
Quinoidimonium salt of 11 (blue) 3 = C1-, SOr--, etc.
I n the present in1 estigation, some comnion nitrates and nitramines used as propellant ingredients were tested with both sulfuric and phosphoric acids. The extent of each reaction mas determined by the nitrometer. These compounds were then tested with diphenylamine in sulfuric acid, and in phosphoric acid. Nitraniines, m-hich gave positive test- n ith the diphenylamine- sulfuric acid reagent, consistently showed negati7-e results m-ith the diphenylamine-phosphoric acid reagent. The test could therefore be used to detect nitrates in the presence of nitramines.
Table I.
Determination of Nitrates and Nitramines Calcd.
Yitrocelluloee, pyro
13.86 13.86 13.86
13.85, 13.85 13.85, 13.85 13.85, 13.85
94 5% HzS04 857,
12 60 12 60
91% Hap04 1: 1 b volume 85% H,P& 94.5% Hgs0-1
12 60 12 60
12 60, 12 61 Reaction about 10% complete after 1 hour Reaction not complete Reaction about 20Y0 complete after 1 hour
+
Kitroguanidine
5 ml. 80% H~SOI
PROCEDURE
Nitrometer. Recrystallized potassium nitrate was used for standardization. T h e gas, nitrogen oxide, vias more soluble in t h e phosphoric acid t h a n in t h e sulfuric b y 0,0370 for a 1-gram sample. The folloning acids (25 ml. for each sample) w r e used: glacial acetic, 94.5 + 0.5% sulfuric acid, 80 i 0.5% sulfuric acid, and 85 ?L 0.5% phosphoric acid. The concentration of the sulfuric acid was determined by titration and that of phosphoric, by density. Diphenylamine Spot Test.
Is SUL-
ACID. T h e ieagent was prepared by dissolving 0.20 gram of recrystallized diphenylamine in 100 ml. of sulfuric acid, 70% b y u-eight. Approximately 0.01 gram of the sample mas dissolved in 1 ml. of 5070 sulfuric acid. The saniple solution n as placed in a small test tube and 0.2 to 0.3 ml. of reagent added so that it formed a layer under the sample solution. The appearance of a blue or purple color at the interface constituted a positive test. IN PHOSPHORIC ACID. For the reagent, 0.20 gram of recrystallized diphenylamine was dissolved in 100 ml. of 85y0by weight phosphoric acid. .4pproximately 0.01 gram of sample was dissolved in 1 nil. of 60% phosphoric acid. The test was carried out as above. except that diphenylamine in phosphoric acid via3 used.
+
20 ml. 94.5% HqSOh
13 46
13 42, 13 41
13.46 13.46
No reaction in 1 hour No reaction in 1 hour
Xitroglycerin
18 42, 18 44
Material insoluble Material insoluble Guanidine nitrate
11 47
11.47 11.47
12.73, 12 83 12 45
Ethylenedinitramine 9 4 . 5 HzS04 8570
18.66 18,66
Fumed off No reaction
Dinitroxyethylnitramine
17,50 17.50
Reaction about 60% complete Reaction about 507, complete
9 4 . 5 7 , HZSOI 85%
11 32, 11 29
FURIC
Tetryl
4.75
Cyclotrimethylenetrinitramine
is formed from the reaction of urea nitrate and guanidine nitrate in the nitrometer. The high and variable results obtained with guanidine nitrate in the present investigation are believed to be due to the formation of nitrous acid (shown b y the appearance of nitrogen dioxide in the generator) and reaction
DISCUSSION A N D RESULTS
The possible use of phosphoric acid for the determination of the more common nitrates and nitramines has been examined (Table I). It is el-ident that for simple inorganic nitrates phosphoric acid may he used. For the organic nitrates and nitramines, either there !vas no reaction or a n incomplete one. The anomalous behavior of guanidine nitrate in the nitrometer reaction was described by Cope and Barab ( 2 ) , who found that values ranging from 13.3 to 15.6% nitrogen were obtained if all the gas formed n-ere taken as nitrogen oxide. According to these authors, some carbon dioxide as w l l as nitrogen
Table II. Results of Spot Testa Diphenylamine In 85Yc In 85y0 H~SOI HaPOa
Compound K?;Os KN02 Kitroglycerin Yitrocellulose Nitroguanidine Tetryl Cyclotrimethylenetrinitramine Ethylenedinitramine Dinitroxyethylnitramine a
f,
positive;
-,
++ +++ + ++ +
negative.
++ ++ $.
4.75 4.75
4 60 Yo reaction No reaction
18.90 18.90 18.90
KO reaction
18 71
KOreaction
of nitrous acid with the amine to form nitrogen. The spot test n-hich was developed consisted of tn-o reagents: diphenylamine in 70% sulfuric acid and in 85% phosphoric acid. These reagents were tested on a number of materials with the results shown in Table 11. This method should have application in the testing of nitramines for the presence of nitrate salts, occluded nitric acid from the nitration process, and nitrate esters. The test is simple, rapid, and suitable for use in the control laboratory. LITERATURE CITED
(1) Becker, W. IT., Shaefer, W. E., in “Organic -lnalysis,” Vol. 11, pp. 71122, Interscience, N e w York, 1954. (2) Cope, W.C., Barab, J., J . A m . Chem. Soc. 38,2552 (1916). (3) Feigl, F., “Spot Tests in Organic Analysis,” 5th ed., pp. 168-70, Elsevier, Y-ew York, 1956. (4)Wieland, H., Bel. 46, 3296 (1913); 52, 886 (1919). RECEIVEDfor review January 8, 1958. Accepted May 10, 1958. Division of Analytical Chemietr 133rd Meeting, ACS, San Francisco, &hif., April 1958. VOL. 30, NO. 10, OCTOBER 1958
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