GALLIUM, so called in honour of France (Gallia), symbol Ga, atomic weight 69 ’ 9, a metal discovered, August 27, 1875, byM. Lecoq de Boisbaudran, in the spectroscopic examination of zinc-blende from Pierrefitte in the valley of Argeles, Hautes Pyrénées, and since found to exist in blende from several other localities, notably in that of the mines of ttidrich and Apfel at Bensberg, on the Rhine, which contains nearly 16 milligrammes per kilogramme. Its density and approximate atomic weight·, and other of its characters, were predicted by Mendeljeff, in accordance with his law that the properties of the elementary bodies, as also the constitution and properties of their combinations, are periodic functions of their atomic weights (see article Chemistry, vol. v. p. 543, col. 2). Gallium may be prepared by a process the chief features of which are the treatment of the ore, which contains the metal in only very minute quantity, with zinc; the removal, from a hydrochloric acid solution of the gelatinous precipitate thereby produced, of various foreign metals by means of hydrogen sulphide; the fractionation of the residual liquid with sodium carbonate, gallium being thrown down before zinc by that reagent; the formation of a sulphate from the resultant precipitate; and, lastly, the electrolysis of a potash solution of the purified oxide obtained therefrom, the metal appearing on the negative platinum electrode. Solid gallium is greyish-white, of octahedral crystallization, and remarkably hard and resistant even at a temperature little below its melting point, and is but slightly malleable and flexible, though thin plates of it will bear bending several times without breaking. It melts when held in the fingers, its point of fusion being 30' ’ 15 C. (86 o, 27 Fahr.). The ...