Germanium
Title: Germanium
CAS Registry Number: 7440-56-4
Literature References: Ge; at. wt 72.61; at. no. 32; valences 4, 2. Group IVA (14). Five naturally occurring isotopes: 70 (20.55%); 72 (27.37%); 73 (7.67%); 74 (36.74%); 76 (7.67%); artificial, radioactive isotopes: 65-69; 71; 75; 77; 78. Extent of occurrence in the earth's crust about 0.0007%. Predicted and called ekasilicon by Mendeléeff. Discovered in 1886 by Clemens Winkler: J. Prakt. Chem. 34, 177 (1886). Obtained industrially from the flue dusts of smelters processing zinc-bearing ores: Jaffee et al., Trans. Electrochem. Soc. 89, 277 (1946). Purification by zone refining: Pfann, J. Met. 4, 747 (1952). Physical properties: Hassion et al., J. Phys. Chem. 59, 1076 (1955). Inhalation toxicity studies: J. H. E. Arts et al., Food Chem. Toxicol. 28, 571 (1990). Review and description of modern isolation techniques: Pirest in L. P. Hunter, Handbook of Semiconductor Electronics (McGraw-Hill, New York, 1956), section 6. Comprehensive monograph: V. I. Davydov, Germanium (Gordon & Breach, New York, 1966) 417 pp. Reviews: Rochow in Comprehensive Inorganic Chemistry vol. 2, J. C. Bailar, Jr. et al., Eds. (Pergamon Press, Oxford, 1973) pp 1-41; J. H. Adams in Kirk-Othmer Encyclopedia of Chemical Technology vol. 11 (Wiley-Interscience, New York, 3rd ed., 1980) pp 791-802.
Properties: Grayish-white, lustrous, brittle metalloid. Diamond-cubic structure when cryst. Poor conductor of electricity. d425 5.323. Reported melting points range from 925-975°; best value 937.2° (Hassion). Vol smaller by a few % when molten. bp 2700°. Thermal expansion coefficient (at ~25°): 6.1 ´ 10-6/°C. Thermal conductivity (at 25°): 0.14 cal/sec cm/°C. Specific heat (0-100°): 0.074 cal/g/°C. Lattice constant at 25°: 5.657 ´ 10-8 cm. Atoms/cc = 4.42 ´ 1022. Volume compressibility: 1.3 ´ 10-12 cm2/dyn. Dielectric constant: 16. Covalent bond ionization energy at 0 K = 1.2 ev. Band gap: 0.67 ev. Impurity atom ionization energy: ~0.01 ev. Intrinsic resistivity at 300 K = 47 ohm-cm. Electron mobility at 300 K = 3900 cm2/v sec. Hole mobility at 300 K = 1900 cm/v sec. Magnetic (mass) susceptibility (c ´ 106) = -0.12. Intrinsic charge density at 300 K = 2.4 ´ 1013. Electron diffusion constant at 300 K = 100. Hole diffusion constant at 300 K = 49. Insol in water, hydrochloric acid, dil alkali hydroxides. Attacked by aqua regia, concd nitric or sulfuric acids, fused alkalies, alkali peroxides, nitrates, or carbonates. Relatively stable, unaffected by air, becomes oxidized above 600°; is slowly oxidized by hydrogen peroxide at room temp, fairly rapidly at 90°; is attacked by hydrogen above 1000°. When finely divided, burns in chlorine or bromine.
Melting point: melting points range from 925-975°; best value 937.2° (Hassion)
Boiling point: bp 2700°
Density: d425 5.323
Use: In electronics: Manuf rectifying devices (germanium diodes), transistors, in red-fluorescing phosphors; in dental alloys; in the production of glass capable of transmitting infrared radiation. Review of uses: Aldington, Cumming, Endeavour 14, 200-204 (1955); New Uses for Germanium, F. I. Metz, Ed. (Midwest Research Institute, 1974) 120 pp.
Therap-Cat-Vet: Astringent (intestinal).

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