Chemical Fact Sheet
Germanium
| Chemical Abstract Number (CAS #) | 7440-56-4 |
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| Analytical Methods | 200.8 - 6020 |
| Molecular Formula | Ge |
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Synopsis
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Germanium - (L. Germania, Germany), Ge; at.wt. 72.61(2); at.no. 32; m.p. 938.25 deg C; b.p. 2833 deg C; sp.gr. 5.323 (25 deg 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 zinc ores, and has been recovered from the by-products of combustion of certain coals. Its presence in coal insures a large reserve of the element in the years to come. Germanium can be separated from other metals by fractional distillation of its volatile tetrachloride. The tetrachloride may then be hydrolyzed to aive GeO2; 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 semiconductor use with an impurity of only one part in 10-10. Doped with arsenic, gallium, or other elements, it is used as a transistor element in thousands of electronic applications. Its application as a semiconductor element now provides the largest use for germanium. 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 detectors. Germanium oxide's high index of refraction and dispersion has made it 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 germanium is about $3/g (99.999% purity). Twenty nine isotopes and isomers are known, five of which occur naturally. |
| Use | IN ELECTRONICS: MANUFACTURE OF RECTIFYING DEVICES (GERMANIUM DIODES), TRANSISTORS, IN RED-FLUORESCING PHOSPHORS; IN DENTAL ALLOYS; IN PRODN OF GLASS CAPABLE OF TRANSMITTING INFRARED RADIATION AS A CATALYST. IN ELECTROPLATING. (VET): INTESTINAL ASTRINGENT. |
| Consumption Patterns | Infrared Optics, 60%; Fiber optics systems, 15%; Detectors, 10%; and Semi-conductors (incl transistors, diodes and rectifiers), 5% (1985 |
| Apparent Color | GRAYISH-WHITE, LUSTROUS, BRITTLE METALLOID; DIAMOND-CUBIC STRUCTURE WHEN CRYSTALLINE |
| Boiling Point | 2700 DEG C |
| Melting Point | 937.2 DEG C |
| Molecular Weight | 72.59 |
| Density | 5.323 @ 25 DEG C/4 DEG C |
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Chemical and Physical Properties |
THERMAL EXPANSION COEFFICIENT AT APPROX 25 DEG C: 6.1X10-6 DEG C; THERMAL CONDUCTIVITY @ 25 DEG C: 0.14 CAL/SEC CM/DEG C; SPECIFIC HEAT (0-100 DEG C): 0.074 CAL/G/DEG C LATTICE CONSTANT @ 25 DEG: 5.657X10-8 CM; VOL COMPRESSIBILITY: 1.3X10-12 SQ CM/DYN; DIELECTRIC CONSTANT: 16; MAGNETIC (MASS) SUSCEPTIBILITY (CHI X10+6)= -0.12 COVALENT BOND IONIZATION ENERGY @ 0 DEG K= 1.2 ELECTRON VOLT; BAND GAP: 0.67 ELECTRON VOLT; ATOMS/CC= 4.42X10+22; IMPURITY ATOM IONIZATION ENERGY: APPROX 0.01 ELECTRON VOLT; INTRINSIC RESISTIVITY @ 300 DEG K= 47 OHM-CM ELECTRON MOBILITY @ 300 DEG K: 3900 SQ CM/V SEC; HOLE MOBILITY @ 300 DEG K= 1900 CM/V SEC; HOLE DIFFUSION CONSTANT @ 300 DEG K= 49 INTRINSIC CHARGE DENSITY @ 300 DEG K= 2.4X10+13; ELECTRON DIFFUSION CONSTANT @ 300 DEG K= 100 IS HIGHLY TRANSPARENT TO INFRARED LIGHT; HAS A HIGH INDEX OF REFRACTION THE METAL & MANY OF ITS ALLOYS EXPAND ON SOLIDIFICATION FIVE NATURALLY OCCURRING ISOTOPES: 70 (20.55%); 72 (27.37%); 73 (7.67%); 74 (36.74%); 76 (7.67%); ATOMIC NUMBER 32 POOR CONDUCTOR OF ELECTRICITY; VOL SMALLER BY FEW % WHEN MOLTEN; ATTACKED BY AQUA REGIA, CONCN NITRIC OR SULFURIC ACIDS, FUSED ALKALIES, ALKALI PEROXIDES, NITRATES, OR CARBONATES HARDNESS 6 ON MOHS SCALE. |
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Environmental Impact |
INDUSTRIAL EXPOSURES ARE TO THE DUSTS & FUMES OF THE METAL & ITS OXIDE DURING THE SEPARATION & PURIFICATION FROM THE ORE CONCENTRATE. CD, PB, & ZN ARE CONCOMITANT EXPOSURES. IN THE ELECTRONICS INDUSTRY, EXPOSURES ARE CONFINED TO METAL FUMES FROM WELDING OR MULTIPLE-ZONE MELTING. EXPOSURE TO GERMANIUM TETRACHLORIDE & ITS HYDROLYSIS PRODUCTS (GEO2, HCL) MAY OCCUR IN PRODN OF GE & ITS COMPD. DUST CONCN RANGING FROM 5 TO 70 MG/CU M (CORRESPONDING TO GE CONCN UP TO ABOUT 7 MG/CU M) OCCUR IN PRODN OF GERMANIUM MONOCRYSTALS. IN SOME CASES CONTAINED UP TO 30% OF FREE SILICA. NO AIR STANDARDS FOR GE HAVE BEEN SET BY AN OFFICIAL AGENCY. INFORMATION HAS BEEN LIMITED TO EXPERIMENTAL STUDY OF THE ELEMENT. NO WORKER EXPOSURE EXPERIENCE HAS BEEN REPORTED. |
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Environmental Fate |
GE IS NOT FOUND IN THE FREE STATE, BUT ALWAYS IN COMBINATION WITH OTHER ELEMENTS. EXTENT OF OCCURRENCE IN EARTH'S CRUST ABOUT 0.0007%. PREDICTED & CALLED EKASILICON BY MENDELEEFF. DISCOVERED IN 1886 BY CLEMENS WINKLER. METAL IS FOUND IN ARGYRODITE, A SULFIDE OF GERMANIUM & SILVER; IN GERMANITE, WHICH CONTAINS 8% OF ELEMENT; IN ZINC ORES; IN COAL; & OTHER MINERALS. ITS PRESENCE IN COAL INSURES LARGE RESERVE OF THE ELEMENT IN YR TO COME. Occurs in significant concentrations in many coals of the world with the highest concentration occuring in the upper and lower few centimeters of the vein. EST 2000 TONS/YR AS AMT DISCHARGED IN STACK GASES, FLUE DUST & ASHES FROM COAL BURNING PLANTS IN UNITED KINGDOM. COAL ASH MAY CONTAIN 20-280 MG GE/KG. OAK & BEECH HUMUS IN ONE LOCALITY IN GERMANY CONTAINS 70 PPM. GERMANIUM OCCURS WIDELY IN FOOD; SEAFOODS SUCH AS CANNED TUNA & DRIED PAN FISH CONTAIN 3 PPM GE, & CANNED TOMATO JUICE & BAKED BEANS CONTAIN ABOUT 5 PPM. GE IS TAKEN UP BY CEREALS, ESPECIALLY OATS FROM GE-BEARING SOILS. OAK & BEECH HUMUS IN ONE LOCALITY IN GERMANY CONTAINS 70 PPM. |
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Atmosphere |
CONSIDERABLE AMT OF GERMANIUM ARE DISCHARGED INTO ATMOSPHERE BY COAL COMBUSTION. EST 2000 TONS/YR AS AMT DISCHARGED IN STACK GASES, FLUE DUST & ASHES FROM COAL BURNING PLANTS IN UNITED KINGDOM. ONE WOULD EXPECT SIGNIFICANT AMT IN URBAN ATMOSPHERE AS RESULT OF RELATIVELY HIGH (1.6 TO 7.5%) GERMANIUM CONCN IN COAL. |
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