TELLURIUM [[[Symbol]] Te, atomic weight 127.5 (0=16)], a chemical element, found to a certain extent in nature in the uncombined condition, but chiefly in combination with other metals in the form of tellurides, such, for example, as sylvanite, black tellurium, and tetradymite.
It is best obtained by decomposing metallic tellurides with mineral acids.
It may be liquefied, the liquid boiling at o° C., and on further cooling, it solidifies, the solid melting at -48° C. Many tellurides of metals have been examined by C. A.
Soc., 1909, 3 1, p. 902) who obtained the sodium and potassium tellurides by the direct union of their component elements and others from these by precipitation.
The ores are almost exclusively gold, tellurides being the most characteristic form, and occur in fissure veins.
Altaite is of interest as being one of the tellurides found associated with gold.
Silver sulphide, Ag 2 S, occurs naturally as the orthorhombic acanthite, and the cubic argentite; the telluride, Ag 2 Te, named hessite, assumes cubic forms; other tellurides containing silver are petzite, (Ag,Au) 2 Te, and sylvanite, AuAgTe 4.