Potassium cyanide (KCN) was a very important source of alkali steel cyanides before the creation with the Castner approach. It was made by the decomposition of potassium ferrocyanide. The reaction is as follows: Though HF is usually named hydrogen fluoride, it's offered another name for emphasis that it's an acid. https://fernandoufxvc.csublogs.com/36780554/not-known-details-about-is-potassium-cyanide-dangerous