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Tellurite is a rare oxide mineral composed of tellurium dioxide (Te O 2).. It occurs as prismatic to acicular transparent yellow to white orthorhombic crystals. It occurs in the oxidation zone of mineral deposits in association with native tellurium, emmonsite and other tellurium minerals.
Tellurite is a oxyanion of tellurium with the formula TeO 2− 3. It is the ion of tellurous acid, and is chemically related to tellurium dioxide (TeO 2), whose mineral appearance also bears the name tellurite. Tellurites are typically colorless or white salts, which in some ways are comparable to sulfite. [3]
Historically the name tellurate was only applied to oxyanions of tellurium with oxidation number +6, formally derived from telluric acid Te(OH) 6, and the name tellurite referred to oxyanions of tellurium with oxidation number +4, formally derived from tellurous acid (HO) 2 TeO and these names are in common use.
The other halogens do not form halides with tellurium in the +6 oxidation state, but only tetrahalides (TeCl 4, TeBr 4 and TeI 4) in the +4 state, and other lower halides (Te 3 Cl 2, Te 2 Cl 2, Te 2 Br 2, Te 2 I and two forms of TeI). In the +4 oxidation state, halotellurate anions are known, such as TeCl 2− 6 and Te 2 Cl 2− 10.
Tellurium dioxide (TeO 2) is a solid oxide of tellurium.It is encountered in two different forms, the yellow orthorhombic mineral tellurite, β-TeO 2, and the synthetic, colourless tetragonal (paratellurite), α-TeO 2. [2]
Most tellurite salts contain the TeO 2− 3 ion. Oxidation of its aqueous solution with hydrogen peroxide gives the tellurate ion. It is usually prepared as an aqueous solution where it acts as a weak acid. [1] [3] H 2 TeO 3 + H 2 O ⇌ H 3 O + + HTeO − 3 K a1 = 2 × 10 −3 HTeO − 3 + H 2 O ⇌ H 3 O + + TeO 2− 3 K a2 = 1 × 10 −8