From the CRC handbook of Chemistry and Physics, CRC Press, Cleveland, 55th ed., 1974-75 "The Elements" by C.R. Hammond. page B-6
GERMANIUM (L. Germania, Germany), Ge; at. wt. 72.59; at. no. 32; m.p. 937.4 C; b.p. 2830 C; sp.gr. 5.323 (25 C); valence 2 and 4. Predicted by Mendeleev in 1871 as ekasilicon, and discovered by Winkler in 1886. The metal is found in argyrodite, a sulfide of germanium and silver; in germanite, which contains 8% of the element; in zinc ores; in coal; and in other minerals. The element is frequently obtained commercially from flue dusts of smelters processing combustion of certain coals. Its presence incola insures a large reserve of the element in the years to come. Germanium can be spearated from other metals by fractional distillation of its volatile tetracholoride. The tetracholoride may then be hydrolysed to give GeO2; then the dioxide can be reduced with hydrogen to give the metal. Recently developed zone-refining techniques permit the production of germanium of ultra-high purity. The element is a gray-white metalloid, and in its pure state 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 semiconcductor use with a impurity of only 1 part in 10^10. Doped with arsenic, gallium and other elements, it is used as a transistor element in thousands of electronic applications. Transistors now provide the largest use for the element, but germanium is alos finding many other applications including use as an alloying agent, as a phosphor in fluorescent lamps, and as a catalyst. Germanium oxide is transparent to the infrared and is used in infrared spectroscopes and other optical equipment, including extremely sensitive infrared detectors. Its high index of refraction and dispersion has made germanium useful as a component of glasses used in 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 of interest as chemotherapeutic agents. The cost of gernanium is about 50 cents/gm. For 99.9+ % purity in small lots.
