Potassium cyanide is the salt of potassium and hydrogen cyanide, a colorless compound with smell of almonds, similar in appearance to sugar and highly soluble in water. Despite being highly toxic, it is one of the few substances that form soluble compounds with gold, and thus is used in jewellery for chemical gilding and buffing . It is also sometimes used in gold mining for chemical extraction of metal from ore (though sodium cyanide is more commonly used).

Physiological effects

As all cyanides, potassium cyanide is a potent poison blocking the cells' electron transport chain by forming a permanent bind with the iron atom in heme of cytochromes. The result is disruption of the cell's breathing process.

The effects of potassium cyanide are similar to sodium cyanide. Once more than 3–4 mg of potassium cyanide is consumed, consciousness is lost within one minute, sometimes within 10 seconds, depending on the strength of the body's immunity and the amount of food present in the stomach. After a span of about 45 minutes, the body goes into a state of coma or deep sleep and the person may die within two hours if not treated medically. During this period, convulsions may occur. Death occurs mainly by cardiac arrest.

The antidote against potassium cyanide poisoning is glucose which can greatly slow down the poison's effect and protect the cells by binding the cyanide competitively. The somewhat legendary immunity of Gregory Rasputin to cyanide was not due to his supernatural powers, but due to the incompetence of his killers: they put poison in sweet pastries and madeira wine, both of which are rich in sugar. Rasputin was administered the poison together with massive quantities of antidote, and did not die until Prince Felix Yusupov shot him. Administering glucose intravenously is an effective measure even after ingestion of potassium cyanide.

Suicide

Potassium cyanide is occasionally used as a means for committing suicide. The drug has been effectively used by soldiers to commit suicide rather than reveal secrets under torture. Both Hermann Göring and Adolf Hitler are reputed to have used cyanide pills or tablets to commit suicide (in Hitler's case, simultaneously with gunshot).