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(sīăn`əjən), NCCN, colorless, flammable, extremely poisonous gas with a characteristic odor somewhat like that of hydrogen cyanide. It melts at −35°C;, boils at −21°C;, and is soluble in water, ethanol, or ether. It is chemically very active.



N≡C—C≡N, the dinitrile of oxalic acid; a colorless gas, with a pungent odor, a melting point of –27.8°C, and a boiling point of –21.15°C. Cyanogen is poorly soluble in water but dissolves more readily in alcohol, ether, and acetic acid. Upon prolonged heating at 400°C, it is converted into the amorphous polymer paracyanogen (CN)x, where x ranges from 2,000 to 3,000; at 800°C, paracyanogen is completely depolymerized. Cyanogen is characterized by pseudohalogen properties; for example, like chlorine, it reacts with aqueous solutions of alkalies:

(CN)2 + 2KOH→KCN + KCNO + H2O

Cyanogen may be produced by the catalytic oxidation of hydrocyanic acid, by the reaction of heated coke with nitrogen, or by the dehydration of the diamide of oxalic acid, (CONH2)2. It is also formed during the pyrolysis of nitrogen-containing organic compounds and thus is found in small amounts in coke gas and blast-furnace gas. Cyanogen has been detected spectroscopically in comets. It is used in organic synthesis.

Although poisonous, cyanogen is less toxic than hydrocyanic acid and its salts—the cyanides.


Brotherton, T. K., and J. W. Lynn. “The Synthesis and Chemistry of Cyanogen.” Chemical Reviews, 1959, vol. 59, no. 5, p. 841.



A univalent radical, CN.
(inorganic chemistry)
C2N2 A colorless, highly toxic gas with a pungent odor; a starting material for the production of complex thiocyanates used as insecticides. Also known as dicyanogen.


an extremely poisonous colourless flammable gas with an almond-like odour: has been used in chemical warfare. Formula: (CN)2