Chemical Fact Sheet
Tellurium
| Chemical Abstract Number (CAS #) | 13494-80-9 |
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| Synonyms | AURUM-PARADOXUM; METALLUM-PROBLEMATUM; TELLUR- (POLISH) |
| Analytical Methods | 200.7 - 200.8 - 6020 |
| Molecular Formula | Te |
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Synopsis
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Tellurium-(L. tellus, earth), Te; at. wt. 127.60(3); at. no. 52; m.p. 449.51 +/- 0.3 deg C; b.p.988 deg C; sp.gr. 6.24 (20 deg C); valence 2, 4, or 6. Discovered by Muller von Reichenstein in 1782; named by Klaproth, who isolated it in 1798. Tellurium is occasionally found native, but is more often found as the telluride of gold (calaverite), and combined with other metals. It is recovered commercially from the anode muds produced during the electrolytic refining of blister copper. The U.S., Canada, Peru, and Japan are the largest Free World producers of the element. Crystalline tellurium has a silvery-white appearance, and when pure exhibits a metallic luster. It is brittle and easily pulverized. Amorphous tellurium is formed by precipitating tellurium from a solution of telluric or telturous acid. Whether this form is truly amorphous, or made of minute crystals, is open to question. Tellurium is a p-type semiconductor, and shows greater conductivity in certain directions, depending on alignment of the atoms. Its conductivity increases slightly with exposure to light. It can be doped with silver, copper, gold, tin, or other elements. In air, tellurium burns with a greenish-blue flame, forming the dioxide. Molten tellurium corrodes iron, copper, and stainless steel. Tellurium and its compounds are probably toxic and should be handled with care. Workmen exposed to as little as 0.01 mg/cu m of air, or less, develop "tellurium breath," which has a garlic-like odor. Forty two isotopes and isomers of tellurium are known, with atomic masses ranging from 106 to 138. Natural tellurium consists of eight isotopes, two of which are radioactive with very long half-lives. Tellurium improves the machinability of copper and stainless steel, and its addition to lead decreases the corrosive action of sulfuric acid on lead and improves its strength and hardness. Tellurium is used as a basic ingredient in blasting caps, and is added to cast iron for chill control. Tellurium is used in ceramics. Bismuth telluride has been used in thermoelectric devices. Tellurium costs about 20 cents/g, with a purity of about 99.5%. The metal with a purity of 99.9999% costs about $2/g. |
| Use | COLORING AGENT IN CHINAWARE, PORCELAINS, ENAMELS, GLASS; PRODUCING BLACK FINISH ON SILVERWARE. SEMICONDUCTOR DEVICES & RESEARCH; MFR SPECIAL ALLOYS OF MARKED ELECTRICAL RESISTANCE. Improve the crop strength of tin and the mechanical properties of lead. AS A CATALYST. TELLURIUM VAPOR IN "DAYLIGHT" LAMPS. MAJOR USE IS IN VULCANIZATION OF RUBBER: USED TO REDUCE CURING TIME & IMPROVE THE CHARACTERISTICS OF RUBBER. In metal finishing, explosives, antioxidants, infra-red transmitting glasses, and in thermo-electric and other electronic devices. |
| Apparent Color | GRAYISH-WHITE, LUSTROUS, BRITTLE, CRYSTALLINE SOLID, HEXAGONAL, RHOMBOHEDRAL STRUCTURE; DARK-GRAY TO BROWN, AMORPHOUS POWDER WITH METAL CHARACTERISTICS |
| Odor | Odorless |
| Boiling Point | 989.9 DEG C |
| Melting Point | 449.8 DEG C |
| Molecular Weight | 127.60 |
| Density | 6.11-6.27 |
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Chemical and Physical Properties |
DIATOMIC IN VAPOR STATE; ATOMIC NUMBER 52, VALENCE 2, 4, 6; IN AIR DISSOLVES IN POTASSIUM HYDROXIDE ELECTRICAL RESISTIVITY AT 19.6 DEG C: 200,000 MICRO-OHMS/CM; REACTS WITH NITRIC ACID, NOT WITH HYDROCHLORIC ACID LINEAR COEFFICIENT OF THERMAL EXPANSION: 16.8X10-6/DEG C; LATENT HEAT OF FUSION: 4.27 KCAL/MOL; HARDNESS (MOHS): 2.3 MAGNETIC SUSCEPTIBILITY AT 18 DEG C: -0.31X10-6 CGS; SPECIFIC HEAT (SOLID): 0.047 CAL/G/DEG C TELLURIUM BURNS IN AIR WITH A GREENISH-BLUE FLAME TO FORM TELLURIUM DIOXIDE COMBINES WITH HALOGENS, DOES NOT REACT WITH SULFUR OR SELENIUM; MODULUS OF ELASTICITY: 6000000 PSI EIGHT STABLE ISOTOPES: 120, 122, 123, 124, 125, 126, 128, 130; REACTS WITH CONCENTRATED OR FUMING SULFURIC ACID |
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Environmental Impact |
TRACE ELEMENT ACCUMULATION IN AQUATIC SYSTEMS FROM COAL CONVERSION EFFLUENTS. MILD TELLURISM OCCURS PRINCIPALLY WHERE FUMES OF TELLURIUM, PROBABLY IN FORM OF HYDROGEN TELLURIDE, ARE GIVEN OFF. |
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Environmental Fate |
PRESENT IN EARTH'S CRUST TO EXTENT OF 0.002 PPM. OCCURS AS TELLURIDES IN COMBINATION WITH METALS IN TETRADYMITE, ALTAITE, COLORADOLITE; FOUND AS DIOXIDE, TELLURITE; FOUND ALSO NATIVE, ASSOCIATED WITH SILVER & GOLD. PRESENT IN SOME SELENIFEROUS SOILS . CONDIMENTS, DAIRY PRODUCTS, NUTS & FISH HAVE HIGH CONCN OF TELLURIUM. Estimated daily intake at about 100 ug. On the basis of results from NAA neutron activation analysis, the skeleton has been estimated to contain more than 90% of the body burden of tellurium, about 500 mg. Normal values are approx 250 ng/l in normal human blood. Values reported for liver, lung and kidney are about 4-21 ppm, 0.04-1 ppm and 0.6-16 ppm (ug/g wet wt), respectively. |
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Disposal |
TELLURIUM & CMPD MAY BE DISPOSED OF IN SEALED CONTAINERS IN A SECURED SANITARY LANDFILL. |
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