LITHIUM (symb. Li; equiv. 7.0; sp. mr. 0.5936) is the metallic base of the alkali lithia, and derives its name from the Greek word lithos, a stone. The metal is of a white silvery appearance and is much harder than sodium or potassium, but softer than lead. It admits of being welded at ordinary temperatures, and of being dravvn out into wire, which, however, is inferior in teliacity to leaden wire. It fuses at 356'. It is the lightest of all known metals, its- specific gravity being little more than half that of water; it decomposes water at ordinary temperatures. It burns with a brilliant light in oxygen, chlorine, and the vapors of iodine and bromine. It is easily reduced from its chloride by means of a galvanic battery. Lithium forms two compounds with oxygen, viz., lithia (known also as lithion or lithon), which'is the oxide of lithium, and a peroxide of lithium whose formula has not been determined.
Lithia, in a pure and isolated state, cannot be obtained. Hydrate of lithia (L0,110) occurs as a white translucent mass, which cicsely resembles the hydrates of potash and soda. The salts of Edda are of sparing occurrence in nature. The minerals.petalite, triphane, lepidolite, and tourmaline contain Mina in combination with silicic acid, while triphyline and amblygonite contain it as a phosphate; it is also present in small quanti ties in many mineral waters.
Carbonate of lithia (LO,CO2) is precipitated when carbonate of ammonia is added to a strong solution of chloride of lithium, and occurs as a white mass with a slight alkaline reaction. At a dull red heat, it melts into a white enamel. It requires 100 parts of water for its solution, but is more soluble in water charged with carbonic acid. The solution of the salt has been strongly recommended in cases of gout and °Tavel, in con sequence of the solvent power which it exerts on uric acid. The sulphae, phosphate, and nitrate of lithia are of uo special importance. Chloride of lithium (LCI+4 aq.) is readily prepared by dissolving the hydrate of lithia in hydrochloric acid, and evaporat ing. It crystallizes in octoliedra, and is one of the most deliquescent 'salts known, It is of importance as being, the source from whence lithium and carbonate of lithia are obtained.
Lithia was discovered in 1817 by Arfvedson. The metal lithium was first obtained in 1822 by Brande, -but nothing was known regarding its propertieu until 1855, when Bunsen and Matthiessen discovered the present method of obtaining it, and carefully investigated its physical and chemical characters.