The detection and identification of war gases : notes for the use of gas identification officers.

Date:
1943
Catalogue details

Licence: Public Domain Mark

Credit: The detection and identification of war gases : notes for the use of gas identification officers. Source: Wellcome Collection.

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    (i) Chlorine: For the identification of chlorine the usual tests, depending either on its oxidising properties (e.g., blue colour with aniline acetate: yellow colour with o-tolidine hydrochloride), or on its power of liberating other halogens from their compounds (é.g., iodide-starch, and bromide-fluorescein papers), are available. (1) Phosgene: and (iii) Diphosgene: These two gases are chemically similar, and can be detected by. means of papers impregnated with a solution of 5 g. p-dimethylamino benzaldehyde and 5 g. diphenylamine in 100 c.c. of alcohol, such papers (used dry) changing colour rapidly from white to yellow or orange in the presence of as little as one part of phosgene in a million parts of air. The papers are, however, somewhat sensitive to light, necessitating storage in the dark, and are not specific, a similar reaction being given by hydrochloric acid and moist chlorine. For the detection of phosgene, therefore, they should be used in conjunction with a guard-tube containing pumice granules impreg- nated with sodium thiosulphate and sodium iodide, which react with and remove the interfering gases. A specific test for phosgene and diphosgene is the formation of a white turbidity or precipitate of diphenyl urea, CO (NHPh),, m.p. 236° C., by passing their vapours through a saturated aqueous solution of aniline. This reaction will detect 0.2 mg. of phosgene, and can be applied quantitatively by weighing the precipitated diphenyl urea after washing and drying at WOae st Both phosgene and diphosgene are rapidly hydrolysed by water, and are _ readily destroyed by reaction with alkalis, amines (particularly hexamine) and alkaline solutions of phenols. | (iv) Chloropicrin._For the detection of chloropicrin, papers impregnated with a 5 per cent. solution of dimethyl aniline in benzene have been suggested, but the colour change (white to yellow) whicn occurs in the presence of chloro- picrin is only marked in strong concentrations, or preferably in contact with the liquid gas. The most characteristic chemical test for chloropicrin is that depending on the formation of nitrite as a product of hydrolysis with alcoholic sodium ethoxide. Other reactions suitable for the identification of chloropicrin include, pyro- lysis in a hot silica tube to form phosgene, nitrosyl chloride, and other products; production of an insoluble precipitate with alcoholic sodium thiophenate solution; and the formation of chloroform as a product of hydrolysis with alcoholic alkali, the chloroform being subsequently identified by its colour reactions with thymol, resorcinol, etc. Chloropicrin is a relatively stable substance, almost insoluble in water, and unaffected by acids and alkalis. It is, however, rapidly destroyed by alcoholic alkali, or alkaline polysulphide solutions, and also by treatment with a hot concentrated aqueous-alcoholic solution of sodium sulphite. The latter re- action can be used quantitatively, by estimation of the chloride produced. (b) Lachrymators.—The lachrymators as. a class are, perhaps, the most difficult of all war gases to identify chemically, though they are, of course, readily detectable by their physiological effects, and in many instances iden- tifiable by their characteristic odours. They are all rapidly destroyed by hydrolysis with alcoholic alkali, and for the most part attacked by strong oxidising agents; and examination of the products of hydrolysis or oxidation is, in many cases, the only satisfactory procedure for their chemical identifica- tion. Formation and characterisation of the usual ketonic derivatives can be used in the case of bromacetone, C.A.P., etc. (i) Xylyl bromide: The following test, depending on the invariable presence of the o-isomer in the mixture, was developed during the war of 1914-18. Oxidation with alkaline permanganate gives the corresponding phthalic acids,
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