what: Potassium Cyanide. Molecular formula: KCN

why: used for: Photography, gold/silver extraction, metal products.

who: produced by various chemical-producing companies around the world.

where: Usually manufactured in Japan, China, Britain or the US.

How: usually produced by mixing hydrogen cyanide with potassium hydroxide and causing a reaction. In earlier times, it was made by decomposing hydrogen ferrocyanide.

when: before 1900s.