Abstract: A process for the preparation of gaseous cyanogen chloride by a procedure involving reaction of hydrogen cyanide with chlorine in the presence of water with formation of hydrogen chloride as a by-product at a concentration of about 10 to 25% by weight and further involving converting by chlorination ammonium chloride, formed through acid-catalyzed hydrolysis of cyanogen chloride and admixed with the hydrogen chloride by-product, to nitrogen trichloride under pressure and at elevated temperature and decomposing the nitrogen trichloride to nitrogen and chlorine thermally or by U.V. radiation.