Lith′ium, a silvery white metal, first discovered in 1817 by Arfvedson as an oxide and first separated as an element by Brande in 1822, is the lightest of known solids, having a specific gravity of only about .585. It occurs widely, but in very small quantities. In meteors and in the sun there are traces of its presence. It is rather softer than lead. The spectrum is an easy test of its presence, as it shows a bright crimson stripe, together with a pale yellow. Commercially it is obtained chiefly from lepidolite, chiefly for use in medicine, e. g., for gout. Lithium readily forms an oxide, and will rapidly decompose water. It forms alkalies like potassium and sodium.