Potassium is an alkali metal element denoted by the atomic symbol K. It has an atomic number of 19, and an atomic weight of 39.0983. It is a soft, silvery-white metal that is brittle at low temperatures. Potassium melts at 145.9°F (63.28°C) and it becomes a gas at it boiling point of 1398.2°F (759°C).

For centuries before elemental potassium was identified, people made use of its compounds. Potassium carbonate, for example, which is found in the ashes of burned wood, is often called potash. This compound was first used by the ancient Romans to make soap. The Chinese used a naturally occurring mineral called saltpeter (potassium nitrate) to make gunpowder. During the 1700s, American colonists made soap, glass, and other products using potassium carbonate derived from wood ashes. To produce just a ton of this chemical required the burning of several acres' worth of timber. In...