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

Date:: 1943

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

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$last war, being first employed by the Germans on April 22nd, 1915, when 168 tons were released on a 4-mile front against British and French Colonial troops at Ypres, causing some 15,000 casualties, a third of which were fatal. It is, as is well known, a gas.of yellowish-green colour, which is readily liquefiable to a yellow liquid boiling at —33°6° C. The gas is approximately 2:5 times as heavy as air, and is soluble in half its own volume of water. It is also soluble in a number of chlorinated hydrocarbons (e.g. carbon tetrachloride, tetrachlorethane, etc.). It is very reactive chemically, acting as a powerful oxidizing agent. It vigorously attacks metals, especially in the presence of moisture; but liquid chlorine, if dry, has no action on steel, whence the possibility of storing it in cylinders, etc. He (b) Phosgene (C.G.) (Carbonyl chloride: COCI,). Phosgene was ex- tensively employed in industry prior to 1914 without any great anxiety about its toxic properties. It was first used in war by the Germans in December 1915, and remained throughout the last war the principal lethal gas. - Under ordinary conditions it is a colourless, non-persistent gas, having a characteristic odour variously described as resembling that of musty hay, putrefying fruit, decaying leaves, etc. It condenses on cooling to a mobile liquid, B.P. 8-2°C. and D, 1°42, which is colourless if pure, though the technical product is usually yellow. It is very readily soluble in organic solvents, in fats and oils, and in various inorganic halides such as arsenious chloride, stannic chloride, sulphur mono- chloride, etc. It is soluble in its own volume of water, but is rapidly hydrolysed to carbon dioxide and hydrochloric acid, especially in the presence of alkali. Like all chloranhydrides it is a very reactive substance, the chlorine atoms being readily replaced by reaction with alcohols, phenols, amines, etc. Reactions of this type were, it may be recalled, originally used for protection against phosgene, the old type PH gas helmet being impregnated with sodium phenate and hexamine. It does not attack metals if dry—whence its use in metal containers—but is very corrosive in the presence of moisture, especially to copper alloys. (c) Diphosgene (Trichloromethyl chloroformate: Cl. COOCCI,), known to the French as Surpalite, and to the Germans as Perstoff, was one of the principal lethal gases used by them in shell during the last war. Diphosgene, when pure, is a colourless, mobile liquid having D. 1-65 and B.P. 128°C. Its vapour pressure at 20°C. is 10-3 mm., so that although considerably more persistent than chlorine or phosgene, it is still volatile enough to be classed as non-persistent. The vapour has an odour resembling that of phosgene, but somewhat more pungent. It derives its name, diphosgene, from the circumstance that it is decomposed into two molecules of phosgene by heat, detonation, etc., and further, reacts with water and amines as if consisting of two molecules of phosgene, It is corrosive to metals when moist, but does not attack steel if dry. (d) Chloropicrin (P.S.) (Trichloronitromethane: CCl,.NO,), known as Klop to the Germans, as Aquinite to the French, and sometimes as Vomiting gas to the British, was first used by the Russians in 1916, and was later extensively employed by the Allies as a constituent of their penetrating NC. mixture (80 per cent. chloropicrin plus 20 per cent. stannnic chloride). When pure it is a colourless, oily, and refractive liquid of D. 1-66 and B.P. 112°C., the technical product being usually yellow. Its vapour pressure at 20°C. is 18:3 mm., so that like diphosgene it is relatively non-persistent, though not so readily dispersed as chlorine and phosgene. The vapour has a characteristic sweetish smell and pronounced lachrymatory properties. Chloropicrin is comparatively insoluble in water (ca. 0°17 per cent. at ordinary temperature) but soluble in organic solvents. It is a stable com- pound, not hydrolysed by water, and unaffected by ordinary acids and alkalis;$

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

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