Tellurates

Tellurates are the salts of telluric acid (orthotelluric acid H ₆ TeO ₆ and metatelluric acid H ₂ TeO ₄ ) and contain the orthotellurate (VI) anion TeO ₆ ⁶⁻ or the metatellurate (VI) anion TeO ₄ ²⁻ . The salts of telluric acid (H ₂ TeO ₃ ) called tellurites are now also called tellurates (IV) with the anion TeO ₃ ²⁻ according to the IUPAC nomenclature rules .

Tellurates (VI) are good oxidizing agents because they can be easily reduced to tellurates (IV) .

Occurrence

With magnolite ( mercury tellurate Hg ₂ ТеО ₄ ), ferrotellurite ( iron tellurate , FeTeO ₄ ) and montanite ((BiO) ₂ (TeO ₄ ) -2H ₂ O.) some tellurates occur naturally as minerals.

presentation

In addition to precipitation from aqueous solution, tellurates can be obtained , for example, via:

${\displaystyle {\ce {H6TeO6 + 2 NaOH -> Na2H4TeO6 + 2 H2O}}}$

can also be obtained by extraction from cooled alkali melts:

${\displaystyle {\ce {H6TeO6 + 6 NaOH ->[570 K][] Na6TeO6 + 6 H2O}}}$

Tellurates can also be produced by reacting metal oxides with the anhydrides of orthotelluric acid ( tellurium trioxide TeO ₃ ) and telluric acid ( tellurium dioxide TeO ₂ ) in molten salts at temperatures above 700 ° C.

Individual evidence

1. ^ AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 101st edition. Walter de Gruyter, Berlin 1995, ISBN 3-11-012641-9 , p. 634.
2. ^ Helmut Schrätze, Karl-Ludwig Weiner: Mineralogie A textbook on a systematic basis . Walter de Gruyter, 2011, ISBN 978-3-11-083686-8 , pp. 598 ( limited preview in Google Book search).
3. ↑ Georg Brauer: Sodium tellurate and sodium orthotellurate . In: Handbook of Preparative Inorganic Chemistry . Ferdinand Enke Verlag Stuttgart, 1954, p. 350 .