Free cyanide

Cyanide (CN^-) most commonly occurs as hydrogen cyanide (HCN) and its salts: sodium cyanide (NaCN) and potassium cyanide (KCN). Cyanides are widely spread in nature, arising from both natural and anthropogenic sources. Cyanides are produced by certain bacteria, fungi, and algae. Hydrogen cyanide is a colourless liquid with a characteristic odour of bitter almonds.