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|Atomic Number:||31||Atomic Symbol:||Ga|
|Atomic Weight:||69.72||Electron Configuration:||2-8-18-3|
|Melting Point:||29.78oC||Boiling Point:||2403oC|
|Uses:||computer memory, semiconductor production|
History(L. Gallia, France; also from Latin, gallus, a translation of
Lecoq, a cock) Predicted and described by Mendeleev as ekaaluminum, and
discovered spectroscopically by Paul Emile Lecoq de Boisbaudran of France in
1875, who in the same year obtained the free metal by electrolysis of a solution
of the hydroxide in KOH.
SourcesGallium is often found as a trace element in diaspore,
sphalerite, germanite, bauxite, and coal. Some flue dusts from burning coal have
been shown to contain as much 1.5 percent gallium.
PropertiesIt is one of four metals -- mercury, cesium, and rubidium -- which can be
liquid near room temperature and, thus, can be used in high-temperature
thermometers. It has one of the longest liquid ranges of any metal and has a low
vapor pressure even at high temperatures.
There is a strong tendency for gallium to supercool below its freezing point.
Therefore, seeding may be necessary to initiate solidification.
Ultra-pure gallium has a beautiful, silvery appearance, and the solid metal
exhibits a conchoidal fracture similar to glass. The metal expands 3.1 percent
on solidifying; therefore, it should not be stored in glass or metal containers,
because they may break as the metal solidifies.
High-purity gallium is attacked only slowly by mineral acids.
UsesGallium wets glass or porcelain and forms a brilliant mirror when
it is painted on glass. It is widely used in doping semiconductors and producing
solid-state devices such as transistors.
Magnesium gallate containing divalent impurities, such as Mn+2, is finding
use in commercial ultraviolet-activated powder phosphors. Gallium arsenide is
capable of converting electricity directly into coherent light. Gallium readily
alloys with most metals, and has been used as a component in low-melting alloys.
HandlingIts toxicity appears to be of a low order, but should be
handled with care until more data is available.
CostsThe metal can be supplied in ultrapure form (99.99999+%). The cost
is about $3/g.