Cyanogen chloride - preparation, physical properties, hydrolysis and sorption on charcoal.

The substance cyanogen chloride was first prepared by Berthollet in 1787 by the action of chlorine on hydrocyanic acid. He called it “oxidized prussic acid”, but did not apply any formula to it. Gay-Lussac(l) in 1815 made a more complete investigation of this compound, assigning it the formula CNCl from a consideration of its chemical properties. He found that cyanogen chloride could be prepared by reacting moist hydrocyanic acid with chlorine, or by the action of chlorine on dry mercuric cyanide. The physical constants determined by him for cyanogen chloride are not accurate, because his product was impure. [...] Cyanogen chloride was used as a war gas in October, 1916 by the French. It was employed alone, and also mixed with AsCl3, which was alleged to stabilize it, under the name “Vivrite”. It has fair lachrymatory action, and is a very toxic substance, poisoning by cyanogen chloride being similar to that of cyanides, but more severe. Owing to its non-persistent character it was difficult to obtain a lethal concentration in the field. Recent interest in cyanogen chloride has been aroused by the discovery that most service respirators offer very limited protection against this gas when the charcoal contains moisture, that is, under ordinary conditions