ANALYTICAL CHEMISTRY
948 proximately the same. On addition to a n acetic acid solution of dinitrotoluene containing an excess of titanous chloride, however, the sodium acetate raised the p H to 2.7, while the sodium citrate raised it only to 0.9. This was also shown by testing the two buffers on the ether extracts of two samples of smokeless powder containing dinitrotoluene. I n Table I, it is shown that 30 ml. of sodium acetate give the same results as 40 ml. of sodium citrate. hccordingly, the former was selected as the better buffer and used in subsequent work. A comparison was made between the buffer method and the regular boiling method, using a sample of dinitrotoluene and the ether extracts from 12 samples of smokeless powder (Tables I1 and 111). CONCLUSION
The use of sodium acetate as a buffer permits the reduction of dinitrotoluene to be made a t room temperature and thereby shortens the usual procedure. Sodium acetate is shown to be slightly preferable t o sodium citrate as a buffer. Results by the
modified method agree closely with those obtained by the iiwd: procedure. ACKNOWLEDGMENT
Most of the experimental work described in this article \vas carried out a t the Sunflower Ordnance Works and the Badger Ordnance Works, operated by the Hercules Powder Conipanr LITERATURE CITED
(1) Becker, W. W., IND. ENG.CHEM., ANAL.ED.,5, 152 (1933). (2) Knecht, E., Ber., 1910, 3455.
(3) Knecht, E., and Hibbert, E., “New Reduction Methods in Volumetric Analysis,” 2nd ed., New York, Longmans, Green and Co., 1925. (4) Kolthoff, I. M., and Furman, N. H., “Potentiometric Titrations,” p. 304, New York, John Wiley & Sons, 1926. (5) Scott, W. W., and Furman, N. H., “Standard Methods of Chemical Analysis,” 5th ed., p. 480, New York, n. Van Nostrand Co., 1939. RECEIVED February 9, 1947.
Determination of Nitro Nitrogen in Nitroguanidine and Cyclot rimethylenetrinitramine D. L. KOUBA, R . C. KICKLIGHTERI, AND W. W. BECKER Hercules Experiment Station, Hercules Powder Company, Wilmington, Del.
The nitro group in nitroguanidine may be reduced by boiling i t with standard titanous chloride solution for 15 minutes. Although the nitro groups in cyclotrimethylenetrinitramine (RDX) are more resistant to reduction, they may by reduced by adding both titanous chloride and ferrous chloride and boiling for 30 minutes.
I
K COSNECTION with the analysis of new explosive com-
positions during World War 11, methods were needed for the determination of nitroguanidine, 02N.NH.C( :NH)NH2, and of cyclotrimethylenctrinitramine, H&.N.N02CH2N.N02CH2N.N02, popularly known as RDX. The former is a mononitro aliphatic compound with explosive properties similar t o those of trinitrotoluene. Cyclotrimethylenetrinitramine is a heterocyclic, trinitro aliphatic compound, also known as cyclonite and Hexogen. It is more brisant than trinitrotoluene and is one of the most powerful of modern high explosives ( I ) . According to Bernthsen and Sudborough (S),nitroguanidine is easily reduced to aminoguanidine. The use of standard titanous chloride for the reduction of nitro nitrogen in explosives is described by Knecht and Hibbert (9), Callan and Henderson (4, English ( 8 ) , and Becker (2). However, little has been published regarding the reduction of nitramines, Jyhere the nitro group is attached to a nitrogen atom. Khen the regular 5-minute boiling method was first applied to nitroguanidine erratic results were obtained. On longer boiling, hydrolysis of the titanous chloride to yield the hydroxide occurred. However, after the acidity was increased and the solution boiled for 15 minutes, good results were obtained; one mole of nitroguanidine required 4 r,oles of titanous chloride. According to Desvergnes ( 7 ) , R D X cannot be analyzed in the nitrometer, because less than five sixths of its total nitrogen is liberated in elementary form. Rathqburg (11) uwd titanous chlo-ide to analyze the “nitration product of heuamethylenetetramine” (RDX), but he neither balanced the equation nor identified the reaction product. He formdated the reaction
+
CIH6iY3(SOn)s 12TiCL --f C3H6S8 Present address. U. 9. Government, Army of Occupation.
As nitroguanidine with one nitro group reacted with four equivalents of titanous chloride, it seemed logical to expect that RDX, with three nitro groups, would require 12 equivalents. An attempt to reduce R D X with titanous chloride solution succeeded only to the extent of about SO%, even on prolonged boiling. Ferrous chloride effected a negligible reduction. When both reducing agents were added to the same sample, strangely enough, the reduction was over 90% complete. By use of 300% excess of titanous chloride, 20 ml. of 0.7 N ferrous chloride, and a 30-minute boiling period, the reduction was made to proceed to 98 to 99% of the theoretical. I n view of these results, it seems likely that Rathsburg used titanous chloride that contained ferrous iron as an impurity. As this article was being written for publication, Cottrell, MacInnes, and Patterson (6) described a procedure in which nitroguanidine waa dissolved in concentrated sulfuric acid and titrated with ferrous sulfate solution. Their method has not been tested in this laboratory. PURITY OF NITROGUANIDINE BASED ON NITRO NITROGEN COXTENT
Tne preparation and standardization of the titanous chloride and ferric alum solutions have been described (41. Weigh accurately 0.09 to 0.11 gram of dry sample into a 300-ml. flask provided with an inlet tube for carbon dioxide. Dissolve the sample in 50 ml. of 1 to 1 hydrochloric acid and sweep out the air. Add 50 ml. of 0.2 .V titanous chloride (about a 150% excess) and reflux the solution for 15 minutes. Titrate the excess titanous chloride with 0.15 S ferric alum solution, adding 5 ml. of 20y0 ammonium thiocyanate near the end point. Make blank determinations to measure reducible impurities in the reagents and apply this correction value in calculating the result. One
949
V O L U M E 20, NO. 10, O C T O B E R 1 9 4 8 Table I. Reduction of Nitroguanidine with Titanous Chloride
Nitroguanidine Uram 0.0841 0,0905 0.1407 0.1476 0,1289 0.1320 0.0900 0.0409
Excess Titanous Chloride
% 230 206 100 88 115 110 208 205
Time of Reflux Min. 10 10 5 5 15 15 15 15
Equivalents of Titanous Chloride Consumed per Mole of Sitroguanidine
Purity of Nitroguanidine
% 3.98 3.99 3.86 3.90 4.00 3.97 4.01 4.01
99.6 99.7 96.4 97.6 99.9 99.3 100.2 100.2
milliliter of 1N titanous chloride is equivalent to 0.02602 gram of oitroguanidine.
A specimen of pure nitroguanidine (recrystallized from water and dried) was analyzed by the foregoing procedure with the results shown in Table I.
Table 11. Reduction of RDX by Titanous Chloride Alone and by a Mixture of Titanous and Ferrous Chlorides
Weight of R D X
Excess TiCla Present
Gam
%
0.1537 0.1443 0.1400 0.1300 0.1500 0.1480 0.1566 0.1500 0,1500 0.1500 0,1086 0.1055 0,1019 0.1000 0.1023 0.1000 0.1028 0.1130 0.1017 0.1017
136 150 161 172 60 52 46 53 53 51 176 209 257 325 315 306 314 331 320 322
0.7 N FeCh .4dded 311. 0 0 0
0
20 20 20 20 20 20 20 20 20 20 20 20 20 20 22 30
Time of Reflux
Eequivalents of TiCla Consumed per Mole of RDX
Purity of R D X
7.00 7.00 7.19 7.39 10.50 11.22 11.09 11.04 11.04 11.14 11.66 11.68 11.86 11.78 11.93 11.88 11.90 11.96 11.84 1;. 81
58.3 58.3 59.9 61.6 87.5 93.5 92.4 92.0 92.0 92.8 97.2 97.3 98.8 98.2 99.4 99.0 99.2 99.7 98.7 98.4
%
Min. 20 20 20 20 5 lo lo 15
20 2o 20 30 30
30 30 30 30 30 30
PURITY OF RDX BASED ON NITRO NITROGEN CONTENT
In addition to standard titanous chloride and fpriic a l u m solutions, 0.7 N ferrous chloride is required. Weigh accurately 0.09 to 0.11 gram of dry sample into a 300Dissolve the sample in 25 ml. of glacial acetic acid and sweep out the air. Add 20 ml. of 0.7 ATferrous chloride and 115 ml. of 0.2 -V titanous chloride. The latter amounts to about 300% excess. Add 25 ml. of 37y0 hydrochloric acid and reflux the solution for 30 minutes. Titrate the excess titanous chloride with 0.15 ferric alum solution, adding 5 ml. of 20% ammonium thiocyanate near the end point. Make blank determinations to determine reducible impurities in the reagents and apply a correction value in calculating the results. One milliliter of 1IV titanous chloride is equivalent to 0.01851 gram of RDX. ml. flask provided with inlet tube for carbon dioxide.
The foregoing procedure was used to determine the purity of a plant sample of R D X , with the results shown in Table 11. SUMMARY
Correct conditions for the quantitative reduction of the nitro groups in nitroguanidine and cyclotrimethylenetrinitramine (RDX) were developed; four equivalents of titanous chloride are required for the reduction of each nitro group present. In the case of R D X , ferrous chloride as well as titanous chloride
must be used to effect complete reduction. iilthough the reactions appear to be stoichiometric, the reduction products were not isolated and equations were not written. LITERATURE CITED
(1) Bebie. J., “Manual of Explosives, Military Pyrotechnics, and Chemical Warfare Aaent,s.” 1st ed., New York, Macmillan Co., 1943. (2) Becker. TV. T V . , IKD. ENO.CHEY.,Ax.4~.Fp., 5 , 162 (1933). (3) Bernthsen, A , , and Sudborough, J. J., Organic Chemistry.” rev. ed., New York, D. Van Nostrand Co., 1933. (4) Butts, P. G.. Meikle, W. J., Shovers, John, Kouba, D. L.. and Becker. TV. W., .$SAL. CHEX.,20, 917 ( 194s). (5) Callan, T., and Henderson, J. A. R., J . SOC.Chem. Ind., 41, 15761 T (1922). (6) Cottrell, T. L., MacInnes, C. A , and Patterson, E. M., Analyst. 71, 207 (1946). (7) Desvergnes, L., Chimie & Industrie, 28, 1035-44 (1932). (8) English. F. L., J . Ind. Eng. Chem., 12. 994-7 (1920). (9) Knecht, E., and Hihbert, E., “New Reduction Methods in Volumetric Analpis,” 2nd ed., New York, Longmans, Green and Go., 1926. (10) Kolthoff, I. 34.. and Furman, N. H., ”Potentiomet,ric Titrations,” New York, John Wiley & Sons, 1926. (11) Rathsburg, H., Ber.. 54B.3183-4 (1921). RECEIVEDFebruary 9, 1947.
Determination of Potassium Perchlorate in Smokeless Powder PC. B. MELDRUM,
J R . , R. 4. CLARKE’, D. L. K O U B i , AND W . W. BECKES
Hercules Experiment Station, Tferczcles Powder C o m p a n y , IVilmington 99, Del.
D
LJRING World War 11, potassium perchlorate was added to certain types of smokeless powder for specific purposes, and
a rapid method for its determination in powder wm needed. Two methods giving satisfactory results have been developed. The first, or explosion-Volhard method, consists in decomposing a ground powder sample by explosion in a Parr stainless-steel calorimeter bomb. The explosion quantitatively reduces the perchlorate to chloride, which may best be determined by Caldwell and lloyer’s (!?) nitrobenzene modification of the Volhard method (’7). The second, or nitric acid-titanous chloride method, is longer and less accurate than the explosion-Volhard method, 1
Present address, Oregon State Collaca, Corvallis, Ore.
but it avoids need for a Parr bomb. It involves decomposition of the powder sample with nitric acid, subsequent removal of nitrir acid and carbon black (if present), and determination of the potassium perchlorate by reduction with titanous chloride. The analysis of perchlorates by reduction with titanous chloride was first suggested by Knecht (3)and used by Knecht and Hibbert (4), who titrated potassium perchlorate in strong sulfuric acid solution, after adding oxalic acid to facilitate the reduction Rothmund and Burgstaller (5),however, did not consider the presence of oxalic acid necessary. Vil’yamovich (6) succeeded in completely reducing potassium perchlorate in strongly acid (sulfuric and hydrochloric) solution by using approximately 4004,
