An unstable explosive acid, HOCN. The compound has the structure H–O–C≡N, and is also called fulminic acid. Its salts and esters are cyanates (or fulminates). The compound is a volatile liquid, which readily polymerizes. In water it hydrolyses to ammonia and carbon dioxide. It is isomeric with another acid, H–N=C=O, which is known as isocyanic acid. Its salts and esters are isocyanates.