Nomenclature
CAS number: 7440-56-4
Description and 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 × 106/°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 × 108 cm. Atoms/cc = 4.42 × 1022. Volume compressibility: 1.3 × 1012 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 (χ × 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.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.
Therapeutic Category (Veterinary)
Astringent (intestinal).