Potassium

Potassium, chemical element, symbol K; for physical constants see Periodic Table. Potassium was discovered by Sir Humphrey Davy in 1807. It was the first metal isolated by electrolysis. It is found mainly as sylvite (potassium chloride) but occurs in many other minerals. It is obtained commercially by electrolysis of the hydroxide. Potassium is a silvery-white, soft, reactive metal of the alkali metal group. It catches fire spontaneously in water and oxidizes rapidly in air and must be stored in a dry oxygen-free liquid such as mineral oil. It is essential to plant growth and is found in most soils. Potassium and its compounds are used in fertilizers, photography, organic synthesis, and heat transfer media.