Fluorine is named from the Latin fleure, flow, and was isolated in 1866. Fluorine occurs chiefly in fluorspar and cryolite, but is rather widely distributed in other minerals. It is a member of the halogen family of elements and obtained by electrolyzing a solution of potassium hydrogen fluoride in anhydrous hydrogen fluoride in a vessel of metal or transparent fluorspar. Fluorine and its compounds are used in producing uranium and more than 100 commercial fluorochemicals, including many well known high temperature plastics. Fluorides are also added to water supplies to prevent dental cavities.