1117
V O L U M E 25, NO. 7, J U L Y 1 9 5 3 present, and carbon formed during the fusion. Alkaline filtration also removes any nickel which may have dissolved during the hydrogen sulfide removal. I t is important that the filtration be carried out before final acidification. The filtrate is neutralized carefully with concentrated nitric acid, and 5 to 10 drops in excess are added. About 20 mg. of sodium sulfite is added to reduce any halate formed during the hydrogen peroxide oxidation or the addition of the nitric acid. The solution is heated to near boiling for 5 to 10 minutes to expel the sulfur dioxide. Any residual sulfur dioxide can be detected by smell. Extended or excessive heating is not recommended. Approximately 10 ml. of 0:’ S silver nitrate is added slowly to the hot solution with stirring. The solution is further heated to coagulate the silver halide. -1fter coagulation, the solution is cooled, and the silver halide is vacuum filtered through a previously weighed, micro Neubauer crucible. The silver halide is washed, dried for one half hour :it 136’ C., desiccated for 20 minutes, and weighed. Volumetric Determination of the Halide. After heating with ! ) e r o d e , the alkaline solution is transferred to a 40-ml. centrifuge tube. Six to eight drops of saturated ferric alum are added, and the solution is centrifuged until clear. The ferric hydroxide formed is a coagulant which removes the carbon and nickel hydroxide from the solution during centrifugation. The clear qolution is decanted into a clean centrifuge tube, and the walls of the centrifuge tube are washed with a fine stream of water. The solution is acidified with nitric acid, using phenolphthalein as the indicator, and 5 to 10 drops of nitric acid in excess are added. Approximately 20 mg. of sodium sulfite are added to reduce any halate present. The centrifuge tube containing the decanted solution is placed in a beaker of hot water and heated to expel the sulfur dioxide. After cooling, an excess of 0.02 IV silver nitrate is added from a microburet. The solution is centrifuged for about 10 minutes, and the clear supernatant liquid is decanted. The centrifuge tube is washed with a fine stream of distilled water without disturbing the silver chloride. The excess silver nitrate is titrated with 0.01 N ammonium t’hiocyanate solution using 10 drops of saturated ferric alum as the indicator.
purity of the compounds was proved by other analysis. The compounds are described in the footnotes. ?;one of the common elements or combination of common elements interfere with the determination. S o difficulty was encountered in the analysis of sodium or potassium salts or compounds containing large amounts of nickel, copper, or iron. Ailthoughthe use of sodium may seem hazardous, it has been used safely in this determination for over a year because of the convenient form supplied by Pierce Chemical Co. and the small amount used in a fusion. Bombs fabricated from stainless steel and copper were found to be unsatisfactory because of the formation of unknown w b stances which complexed Rith silver ion. The exact nature of the interfering substance or means of eliminating the intixilerence was not investigated because niche1 T\ as found to bc :i .,iti*lac.tory mptal for fabrication of the bomb. ACKNOWLEDGMENT
The authors wish to acknowledge the guidance of I,. 7’.Hallett during the development of this method and the preparation of the manuscript. LITERATURE CITED
(1) Burger, K., Angew. Chem., 54, 479 (1941).
(2) Elving, P. J., and Liggett, W. B , IND. ENG.CHEif., .~s.%L. ED., 14,449 (1942). (3) Grodsky, J., ANAL.CHEM.,21, 1551 (1949). (4) Hallett. L. T., IND.ESG. CHEM.,- ~ N A L .ED.,10, 111 (1938). ( 5 ) Kimball, R. H., and Tufts. L. E., ASAL. CHEM.,19, 150 (1947). (6) hlacxevin, W. If.,and Baxley, W .H., 1x0. ENG.CHEY.,ANAL. E D . , 12,299 (1940). (7) Milton, R. F., and Waters, W.A., “JIethods of Quantitative AIicroanalysis,” p. 91, Kew York, Longmans, Green and Co , Inc., 1949. ( 8 ) Kiederl, J. B., and Kiederl, V.. “Organic Quantitative Microanalysis,” p. 165, 2nd ed., Sew Tork. John Wiley &- Sons, 1942. (9) Ibid., p. 151. (10) Steyermark, A., and Faulkner, 121. B., J . Assoc. Ofic. Agr. Chemists, 35,291-304 (1952). (11) Sundberg, 0. E., and Roycr, G. L., ;isar.. CHEW.,18, 719 (1946). (12) White, L. M., and Kilpatrick, 31. D., I b i d . , 22, 1049 (1950).
DISCUSSIOY OF RESULTS
The results of some of the compounds analyzed are summarized i n Table I. Benzylisothiourea hydrochloride and o-chlorobenzoic acid are not thermally stable compounds. They were analyzed because their purity had been established by independent data. The former compound was used in the collaborative study of Steyermark and Faulkner (fO),and the latter compound has been used in this laboratory as a standard for the past 9 years. Most of the chloro compounds were chosen because of their stability. The
R E C E I V Efor D review October 9, 1952.
Accented January 6, 1933.
Determination of Substituted Triazenes L. J. LOHR1 Central Research Laboratory, General Aniline & F i l m Corp., Easton, Pa. micromethod of Pierce and Rising ( 2 ) adapted from a proTcedure in Houben-I\.e~-l gives an excellent analysis of pure HE
? R,--s=s-S-R~
(1)
aryl-suh~titutrd triazenes hut is not readily adapted to the analysis of samplm which are solutions, slurries. or pastes. Substituteti triazenes in any physical form have been analyzed in this laboixtory using the apparatus and a modified procedure for determini tig organic hydrazines descrihed hy Siggia and Lohr (3). Some of the excellent work by Pierre and Rising has heen confirmed. and the analysis has been extended to include other substituted tt,i:m>nes. Triazenes decompose and liberate nitrogen quantitativelj by the folloning reactions:
H I €I
