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For wide-angle lenses.
(Latin Germania, Germany) Mendeleev predicted the existence of Germanium in 1871 as
ekasilicon, and the element was discovered by Winkler in 1886.
The metal is found in
- argyrodite, a sulfide of germanium and silver ;
- germanite, which contains 8 percent of the element;
- zinc ores;
- coal; and
- other minerals.
The element is commercially obtained from the dusts of smelters processing zinc ores,
as well as recovered from combustion by-products of certain coals. A large reserve of the
elements for future uses in insured in coal sources.
Germanium can be separated from other metals by fractional distillation of its volatile
tetrachloride. The techniques permit the production of germanium of ultra-high purity.
The element is a gray-white metalloid. In its pure state, the element is crystalline
and brittle, retaining its luster in air at room temperature. It is a very important
semiconductor material. Zone-refining techniques have led to production of crystalline
germanium for semiconductor use with an impurity of only one part in 1010.
When germanium is doped with arsenic , gallium , or other elements, it is used as a
transistor element in thousands of electronic applications. The most common use of
germanium is as a semiconductor. Germanium is also finding many other applications
including use as an alloying agent, as a phosphor in fluorescent lamps, and as a catalyst.
Germanium and germanium oxide are transparent to the infrared and are used in infrared
spectroscopes and other optical equipment, including extremely sensitive infrared
The high index of refraction and dispersion properties of its oxide's have made
germanium useful as a component of wide-angle camera lenses and microscope objectives.
The field of organogermanium chemistry is becoming increasingly important. Certain
germanium compounds have a low mammalian toxicity, but a marked activity against certain
bacteria, which makes them useful as chemotherapeutic agents.
The cost of germanium is about $3/g.
Sources: CRC Handbook of Chemistry
and Physics and the American Chemical Society.