C1CN, a colorless gas under ordinary conditions, with a melting point of –6°C and a boiling point of 13°C. In the presence of hydrogen halide acids, cyanogen chloride undergoes trimerization, forming cyanuric chloride. It is produced by the action of chlorine on an aqueous solution of Na₂[Zn(CN)₄], as well as by the reaction of chlorine with an aqueous solution of HCN. It is used in the production of cyanamide, which is a starting material in the production of dicyandiamide and melamine; it is also used in the production of several dyes. Cyanogen chloride is toxic; the presence of even small amounts in the air at places of work induces lacrimation.