A N A L Y T I C A L CHEMISTRY
978 present in t h e standard double-base p o der ~ raises the percentage obtained for triacetin in the total powder analysis by O.O-iCc. An effort was then made t o determine the amount of acidic impurities other than dinitroglycerol. Synthetic double-base powder samples with and without nitroglycerin (and xithout triacetin in both cases) were piepared and tested by the proposed procedure.
Table 111. Dinitroglycerol Content of Synthetic and Standard Double-Base Powder Samples (Ferrous sulfate-titanous chloride method for nitroglycerin) Per Cent DSG (Calcd. as Triacetin) Replica Synthetic Standard 0.04 0 03 0 05 -41.. 0 . 0 4
0.03 0.02 0.06 0.04
T h e results in Table IV indicate t h a t the dinitroglycerol in the nitroglycerin accounts for only one half of t h e total acid impurities. T h e total acid impurities were found t o add 0.087, t o the value obtained for triacetin in the total powder analysis, which appears t o compensate for the O.OSC/, loss of triacetin during the eluate evaporation stage of the procedure. On the basis of this investigation neither a correction factor for acidic impurities nor a recovery factor for triacetin \vas used in the proposed procedure.
Table IV. Acidic Impurities in Synthetic Double-Base Powder without Triacetin by Chromatographic-Acid Hydrolysis Method
Replica
yo .4cidity (Calcd. as TA) in Total ilnalysis of Powder With Without 0.50 gram of nitroglycerin nitroglycerin
1 2 3
0.03 0.03 0.03 0.04
4
0.05 Av.
0.04
0.09
0.07 0.07
0.07 0.08
0.08
The increase in the value obtained for TA due t o the presence of dinitroglycerol and other acid impurities adds 0.08% t o the total analysis percentage.
A considerable quantity of a nitrate compound was found in the methylene chloride extract. Reports received by the authors have identified the nitrate in a similar experiment as nitrocellulose t h a t had been extracted by the methylene chloride and adsorbed a t the top of the chromatographic column. T h e material remained a t the top of the column during the development and ether-elution operations. After six consecutive determinations had been made, this accumulation reached such proportions as t o necessitate repacking the column with fresh adsorbent. Before the adsorbent could be reclaimed, i t was necessary t o extrude and discard this contaminated upper portion. Figure 1 shows the relative positions of the various materials on the column after development with methylene chloride. T h e use of a Soxhlet tube of 25- t o 40-ml. capacity permits a siphoning cycle of 1 t o 2 minutes over a steam b a t h ( 2 ) . Consequently, a 4-hour methylene chloride extraction (instead of the usual 16 hours) is sufficient. Determinations may be made within 2 hours after extraction, and the entire analysis may be completed within 6 hours. I n a determination of the triacetin in a double-base powder sample, the following results were obtained :
Triacetin, OC
Rep1i c n 1
2 3
? Average
Range
Standard deviation
9 9 9 9 9 9 0 0
41 44
45 54 54 48
13 06
The range and standard deviation shown indicate a satisfactoi y degree of precision. T h e procedure 1%as originally developed for propellant formulations containing dioctyl phthalate, 2-nitrodiphenylamine, and a fatty acid salt in addition t o nitroglycerin and nitrocellulose. l l a n y other ingredients commonly found in double-base propellants do not appear to offer interference Compounds specificaally tested (by adding known amounts t o the methylene chloride extract of t h e propellant) and shown t o be without effect include ethyl centralite and dibutyl phthalate. Other ingredients such a6 diphenylamine and dinitrotoluene present no problem, as they pass completely through the column with the nitroglycerin component during development. LITERATURE CITED
(1) Becker, W. W., IND.ENO.CHEM.,ANAL.ED. 5, 152-4 (1933). (2) Corey, R. B., Dekker, A. O., Malmberg, E. W.. LeRosen, 4. L., Schroeder, W. A,, Office of Scientific Research and Development, Division 8, NDRC, OSRD Rept. 1837, 35 (1943). (3) French, J. C., hlosely, B. P., Hercules Powder Co., Kenvil, N. J., “Determination of Diethylphthalate (DEP), Triacetin (TA) and Ethyl Centralite (EC) Plus Diphenylamine (DP-4) in Admixture by Chromatographic Separations-Kenvil Methods,” Smokeless Powder-Analytical AIethods, Rept. Invest. 3112 (Aug. 1, 1952). (4) Geitel, A. C., J . prakt. Chem. 55, 417 (1897). (5) Ibid.,57, 113 (1898). (6) Joint Army-Savy-Air Force Analytical Chemistry Panel for Solid Propellants, hIichelson Laboratory, Naval Ordnance Test Station, China Lake, Calif., Report of Round Robin on Determination of Triacetin, private communication, LIarch 23, 1955. ( i )Kight, W. E., Hercules Powder Co., Allegany Ballistics Laboratory, Cumberland, bId., “Determination of Triacetin in Double-Base Propellant,” private communication, April 15, 1954. (8) Xeyer, J., 2. physik. Chem. 66, 81-125 (1909). (9) Pauling, L., Office of Scientific Research and Development, Division 8, NDRC, OSRD Rept. 5952, 18 (1945). (10) Ibid.,p. 72. (11) Winter, L. S., Butts, P. G., Liberty Powder Defense Corp., Badger Ordnance Works, “Distillation Method for Determination of Triacetin in Double-Base Propellant Powders,” Lab. Dept. Project 6005 (3Iarch 17, 1953). (12) Yamasaki, E., J. A m . Chem. SOC.42, 1455 (1920). R E C E I V Efor D review October 5 , 1955. Accepted March H, 1956. The opinions or asscrtations contained in this article are the private ones of the writers and are not t o be construed as official or reflecting the views of the Navy
Department.
Electron Microscopy-Correct
ion
I n t h e review on “Electron Microscopy” [Swerdlow, Max, Dalton, A. J., Birks, L. S., ANAL.CHEM.28, 597 (1956)l the Literature Cited should be listed as follows: (200) Rhodin, J., Ezptl. Cvll Research 8 , 572 (1955). (201) Rhodin, J., Monograph, Aktiebolaget Godvil, Stockholm, 1954. (202) Rhodin. J . , Dalhamn, T., Ezptl. Cell Research 9, 371 (1955). On page 604, second column, second paragraph, third line and sixth from last line, on page 605>last line, and on page 607, second column, sixth line, (202) should be changed t o (201). On page 607, first column, third and seventh lines of last paragraph, (201) should be changed t o (200). Page 606, second column, second paragraph, second line, (200) should be changed to (202).
