Gallium

Gallium (sym. Ga, eq. 69.8) is a metal discovered by M. Lecoq de Boisbaudran in 1875 in a zinc-blende found in the Pyrenees. It has also been found in blendes from Asturia and from Bensberg. Strange to say, its properties and its salts were predicted before its existence was known by Mendeleëff, in virtue of his Periodic Law (see ATOMIC THEORY, Vol. I. p. 552). Gallium is of a bluish-white colour, and has a specific gravity of 5.9. It possesses the remarkable property of fusing at 30.1° C. (76° F.), and remaining liquid when cooled down even to 0°. If, however, the globule of molten metal be touched with a fragment of solid gallium, it at once solidifies. Heated to bright redness in contact with air gallium does not volatilise, and only a very thin coat of oxide is formed on the surface. Gallium, which has no industrial importance, dissolves readily in hydrochloric acid and in caustic potash with evolution of hydrogen. It forms one oxide, Ga₂O₃, which is insoluble in water, but soluble in potash and ammonia. The chloride, nitrate, and sulphate are all very soluble in water; the sulphate combines with ammonium sulphate to form an alum.