The element discovered in 1807 by Humphry Davy through electrolysis of potash was potassium. Davy used electricity from a voltaic pile to decompose molten caustic potash, now known as potassium hydroxide, or KOH. The experiment produced small globules of a new, highly reactive metal.
Potassium was the first metal isolated by electrolysis. Its discovery demonstrated that electricity could split compounds that resisted ordinary chemical methods and helped establish electrochemistry as a field. Davy also isolated sodium in 1807, and in 1808 used related experiments to obtain calcium, strontium, barium, magnesium, and boron.
Potassium has the symbol K and atomic number 19. The symbol comes from kalium, the Latinized name associated with potash, while the English name reflects its connection with potash. It belongs to the alkali metals and reacts vigorously with water, producing heat, hydrogen gas, and potassium hydroxide.
Potassium is commonly confused with sodium because both are soft, reactive alkali metals and Davy isolated them in the same year. Unlike metallic potassium, potassium ions are essential nutrients in cells, nerves, and muscles and occur widely in minerals and fertilizers.