Cy*an"o*gen (s?-?n"?-j?n), n. [Gr. ky`anos a dark blue substance + -gen: cf. F. cyanogène. So called because it produced blue dyes.] (Chem.) A colorless, inflammable, poisonous gas, C₂N₂, with a peach-blossom odor, so called from its tendency to form blue compounds; obtained by heating ammonium oxalate, mercuric cyanide, etc. It is obtained in combination, forming an alkaline cyanide when nitrogen or a nitrogenous compound is strongly ignited with carbon and soda or potash. It conducts itself like a member of the halogen group of elements, and shows a tendency to form complex compounds. The name is also applied to the univalent radical, CN (the half molecule of cyanogen proper), which was one of the first compound radicals recognized.

&fist; Cyanogen is found in the commercial substances, potassium cyanide, or prussiate of potash, yellow prussiate of potash, Prussian blue, Turnbull's blue, prussic acid, etc.

• A colourless, poisonous gas used as a rocket propellant, an insecticide and in chemical warfare
  
• (chemistry) The pseudohalogen (CN)2 or the radical -CN