With the discovery of substances where the CN radical was not so tightly bound - the gas hydrogen cyanide, hydrocyanic acid, and simple salts like potassium and sodium cyanide - it was soon realized that cyanide was extremely toxic to animal cells. By destroying the mitochondria, an essential element within each cell, the CN radical caused rapid cellular death. This causes a red complexion as cells are unable to utilise oxygen in the blood, and death is by cerebral anoxia.
In 1921, cyanide gas (hydrogen cyanide, HCN) was proposed as a humane method of execution and led to the passage of the ‘Humane Death Bill’ in Nevada. The gas was first used to execute Gee Jon in 1924. Since that time nearly 1000 people have died in the execution gas chambers in the US. All gas chambers used the same method to produce cyanide gas. Pellets of sodium cyanide were dropped into sulfuric acid to release the gas which then enveloped the prisoner.
Hydrogen cyanide is a volatile liquid and can be stabilised and absorbed onto a substrate. In this form (Zyclon B), it was used by the Nazis during the Holocaust. Originally developed as an insecticide, the pellets were kept in sealed containers. When the pellets came into contact with air, HCN gas was released.
Today, cyanide compounds are widely used in industry. Vast quantities of the cyanide salts are produced for use in the gold mining, metallurgy, electroplating and photographic industries. Their toxicity is well known and despite the large quantities used, they remain heavily restricted and difficult to obtain.