Determination of Chlorine in Organic Compounds I. A Rapid Lamp Method WILLIAM MARIAS MALISOFF, School of Medicine, University of Pennsylvania, Philadelphia, Pa.
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cent level, where the determinations are good t o 2 to 3 per cent. Therefore, since burning about 1 gram suffices, a determination can be carried out with only a few milligrams of a substance. The results for phenyl chloride tend to be slightly low, the effect rising t o about 4 per cent a t the highest concentration used. The results for carbon tetrachloride are slightly high in every case, but to the extent of only 1 per cent, and this may be attributed to difference in volatility. The other chlorine compounds have not been studied in detail, but the author hopes that further experience will lead to better adjustments. For example, the low solubility of hexachlorobenzene in naphtha led t o crust formation and some erratic results, a good average being, jn his opinion, more or less of an accident. Furthermore, smoky experiments should probably be discarded, although they were included in this report. The fact that check values have been obtained for the combustion of compounds containing bromine, iodine, and nitrogen, although they are quite different from the amounts actually introduced, raises some hope for further study of the proper conditions of combustion to insure complete conversion to acids. The addition of hydrogen peroxide to the carbonate absorber is a possible method in the author’s opinion, judging from the known reducing action of peroxides on free halogens. The author’s 112 determinations are in general accord with 43 determinations reported by Wirth and Stross (6) on amyl chloride, amylene dichloride, benzyl chloride, butyl chloride, carbon tetrachloride, dichlorobenzene, ethylene dichloride, isopropyl chloride, isobutyl chloride, and propyl chloride, in gasoline to chlorine concentrations of 0.017 to 0.390 per cent, by the use of Mohr’s method of titration with silver nitrate following the combustion. Bowman (2) also uses a combustion method, determining chlorine nephelometrically and finding it necessary to ash the wick. Miloslavsky and Vepritzkaya (4) have carried on some combustions of alcoholic solutions, catching the hydrochloric acid in silver nitrate and titrating the excess silver nitrate with potassium thiocyanate. Using a Kennedy lamp (S), similar to the standard, Smith (5) records a few satisfactory determinations of chlorine in pinene hydrochloride and in mono- and dichlorobenzene dissolved in turpentine, by a silver chloride determination of the absorbed products of combustion. The author’s work indicates that a simple titration is sufficient when dealing only with chlorine. Specific applications must await empirical trial, since no general rule can be given on the basis of several compounds.
Tu’ THE course of a study of the decomposition of organic
sulfur compounds by means of aluminum chloride, it was noted that the sulfur values rose above 100 per cent as determined by the well-known lamp method for the determination of sulfur (1). Suspicion fell on chlorine as the cause, and led to the confirmation that many organic chlorine compounds form hydrochloric acid practically quantitatively on combustion under the conditions of the method. Under more restricted conditions other types form hydrobromic, hydriodic, and nitric acids along with the free halogen. This paper presents data with particular attention to carbon tetrachloride and phenyl chloride, which were used for studying the principal factors.
Experimental GENERAL PROCEDURE. The organic compound is dissolved in a combustible solvent in various concentrations, preferably to produce 0.2 to 0.3 per cent chlorine, and is burned in the standard sulfur lamp following the precautions officially recommended b y the A. S. T. M. (1). The titrations are made with precisely the reagents specified by the method with the same indicator. About 1 gram of solution is burned. The standard calculation may be used and a correction applied-namely, that 1 per cent of sulfur is equivalent t o 2.216 per cent of chlorine. TABLE I. DETERMINATION OF CHLORINE Solvent
Compound
Halogen Calculated
Halogen Found
% Extraction naphtha
Phenyl chloride
Methanol Extraction naphtha
Phenyl chloride Carbon tetrachloride
Methanol
Carbon tetrachloride Ethylene Chlorohydrin o-Chlorophenol Hexachlorobenzene Epichlorohydrin Ethylchloroacetate Chloroacetone Ethylenedibromide E t h 1 iodine Hyzazobenzene Isoamyl nitrite
Methanol Extraction naphtha
Methanol
KO. of Observations
%
0.069 0.121 0,124 0.276 0.524 0.200 0.072 0.130 0.260 0.390 0.520 0.200
0.069 0.121 0.123 0.273 0.504 0.196 0.073 0.132 0.263 0.394 0.522 0.203
f 0.002 f 0.002 0.004 f 0.004 zt 0 . 0 0 5 f 0.003 f 0.002 f 0.002 i 0.003 f 0.004 f 0.005 0.003
6 7 10 8 8 4 8 10 8 7 6 4
0.353
0.345 i 0.005
2
0.177 0.068 0.168 0.256 0.162 0.427 0.273 0.015 0.195
0.176 0.069 0.178 0.270 0.168 0.277 0.302 0,009 0,163
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2 f 0 , 0 0 7 4, crusts f 0.005 2 f 0 . 0 1 0 4, smoke f 0,010 4, smoke i 0.004 2 f 0.005 2 i 0.002 2 f 0.003 2
Discussion
Literature Cited Materials, “Tentative Standards,” 1927; Bur. Mines Tech. Paper 323B (1927). (2) Bowman, S.,J . Znst. Petroleum Tech., 7, 334-8 (1921). (3) Kennedy, INDENG.CHEM.,20, 201 (1928). (4) Miloslavsky and Vepritekaya, J . Applied Chem. (U. S. S . R.),
The choice of a hydrocarbon solvent should fall on a petroleum fractioii relatively free of sulfur and somewhat lighter than gasoline. The material used in this investigation contained 0.018 per cent sulfur. The analysis was checked a t 5 points in the investigation, so that the value is an average of 10 determinations to within 0.001 per cent. This served as a blank correction. In the case of methanol the blank correction was zero. The lamp method operates best in solutions ],ess concentrated than 0.5 per cent, preferably a t the 0.1 to 0.3 per
(1) Am. SOC. Testing
5 , 860-7 (1932).
c.,
( 5 ) Smith, w. ISD.ENQ.CHEnt., Anal. Ed., 3, 364 (1931). (6) Wirth, Chas., 111, and Stross, M. J., Zbid., 5, 85-7 (1933).
RECEIVED August 3, 1935. Presented before the Division of Organic Chemistry a t the 89th Meeting of the American Chemical Society, New York, N. Y., April 22 t o 26, 1935. Work done under grants of the Josiah Macy. Jr., Foundation.
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