lightest of the solid elements, this soft, white metal is found in minerals such as petalite and spodumene. Large deposits are found in North Carolina, Nevada, and California. It imparts a crimson color to flame and floats on water. Chemically active, its compounds have many uses, including lithium carbonate in treating manic-depressive psychosis. Other compounds are used as thickeners in lubricating greases, as brines for refrigerating and air-conditioning systems, and in dry cells and storage batteries. It was discovered in 1817 by Johan August Arfwedson.