Potassium cyanide is a compound with the formula KCN. It is a colorless salt, similar in appearance to sugar, that is highly soluble in water. Most KCN is used in gold mining, organic synthesis, and electroplating. Smaller applications include chemical gilding and buffing of jewelry. Potassium cyanide is highly toxic, and a dose of 200 to 300 milligrams will kill nearly any human.