Gallium, a chemical element. In its solid form, gallium is a bluish-gray metal; as a liquid, it resembles mercury. Gallium is widely distributed in the earth, but only in small amounts. Zinc and aluminum ores are treated to obtain gallium, and the pure metal is expensive. Gallium has a low melting point and a high boiling point, making it useful in quartz thermometers that record temperatures as high as 1,800 F. (982 C.). Gallium was discovered in 1875 by a French chemist, Lecoq de Boisbaudran.
Symbol: Ga. Atomic number: 31. Atomic weight: 69.72. Specific gravity: (solid) 5.90; (liquid) 6.09. Melting point: 85.6 F. (29.8 C.). Boiling point: 4,357 F. (2,403 C.). Valences: +2, +3. Gallium belongs to Group III-A of the Periodic Table.