Potassium a chemical element necessary to the working of living cells; it plays a role in the conduction of nerve signals. In the pure form potassium is an inflammable metal which combines readily with other elements, and it is always found in compounds such as potassium chloride, an impurity in sea salt; and potassium nitrate, saltpetre. The Latin-looking name of the element is actually a back formation from ‘potash’, potassium carbonate originally obtained by heating wood ash with water in earthenware pots (see lye).
