Free Web Hosting Provider - Web Hosting - E-commerce - High Speed Internet - Free Web Page
Search the Web

   Te

TELLURIUM

(L. tellus, earth )

Te  at. wt. 127.60
     at. no. 52
     m.p.   449.5±0.3°C
     b.p. 989.8±3.8°C
     sp. gr. 6.24
     valence 2, 4, or 6.

Tellurium was discovered by Mflller 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 sdlution of telluric or tellurous acid. Whether this form is truly amorphous, or made of minute crystals, is open to question. Tellurium is a p-type semi- conductor, and shows greater conductivity in certain direc- tions, 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 meter of air, or less, develop "tellurium breath", which has a garlic-like odor. Twenty-one isotopes of tellurium are known, with atomic masses ranging from 115 to 135. Natural tellurium consists of eight isotopes, one of which, Te127, is unstable. It is present to the extent of 0.87% and has a half-life of 1.2 x 1013 years. Tellurium improves the machinability of copper and stainless steel, and its addition to lead decreases the corrosive action of sulfuric acid to 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. One such device, using two Bi-Te semiconductors, is reportedly capable of freezing or boiling water in seconds with the power from two flashlight batteries. The unit is said to be capable of bringing the temperature down to - 750C, using only two amperes of current. Tellurium with a purity of 99.7% costs about $6/lb. It is also available with purities of 99.999 + % at a cost of $20 to $30/lb.

Return to periodic table

© 1999 F. Davies
Delphi O.E.M. Co.
All rights reserved