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.