Chemical elements
  Tellurium
    Isotopes
    Energy
    Production
    Physical Properties
    Chemical Properties
    Physiological_Action
    Atomic Weight
    Alloys
    Detection
    Estimation
    Compounds
      Hydrogen Telluride
      Tellurium Tetrafluoride
      Tellurium Hexafluoride
      Tellurium Oxyfluorides
      Tellurium Dichloride
      Tellurium Tetrachloride
      Tellurium Perchlorate
      Tellurium Dibromide
      Tellurium Tetrabromide
      Tellurium Oxybromides
      Tellurium Tetra-iodide
      Tellurium Monoxide
      Tellurium Dioxide
      Tellurites
      Tellurium Trioxide
      Telluric Acids
      Tellurates
      Tellurium Disulphide
      Tellurium-Sulphur Sesquioxide
      Tellurium Sulphates
      Telluropentathionic Acid
      Tellurium Nitride
      Tellurium Nitrite
      Basic Tellurium Nitrate
      Carbon Sulphidotelluride
      Tellurium Dicyanide
    Application
    PDB 1el7-4fon

Tellurites






The alkali tellurites are obtainable from the dioxide by treatment with an aqueous solution of an alkali hydroxide or carbonate or by fusion with an alkali carbonate. They are soluble in water and the other tellurites can be prepared from them by precipitation, those of the alkaline earths being sparingly soluble, the remainder even more sparingly soluble.

In composition, the salts are not all closely related to the monohydrated acid, H2TeO3, although many are derived from this acid. Other salts are known which appear to be derived from hypothetical condensed acids of composition H2Te2O5, ditellurous acid, and H2Te4O9, tetratellurous acid, which may be regarded as products of the partial dehydration of the normal acid, H2TeO3, or as intermediate products in the hydration of tellurium dioxide.

The tellurites in aqueous solution are not very stable, being decomposed by hydrogen sulphide or atmospheric carbon dioxide and undergoing oxidation when treated with oxidising agents such as the permanganates, the halogens or hydrogen peroxide, with formation of tellurates.

They are also reducible to tellurium by dextrose, by sodium hydrosulphite and by electrolysis.

On heating to a temperature of 440° to 470° C. in air, tellurites undergo oxidation, although under these conditions tellurium dioxide is not oxidised nor do the tetratellurites undergo oxidation. In the case of potassium ditellurite the oxidation results in the formation of a compound having the composition K2O.TeO3.TeO2.

With the exception of magnesium tellurite the precipitated tellurites are flocculent and show no tendency to crystallise. The following tellurites have been prepared:

Barium Tellurite, obtained by precipitation from barium chloride solution; the precipitate appears to occlude large quantities of the chloride.
Cadmium Tellurite, 3CdTeO3.2H2O.
Cobalt Tellurite, CoTeO3.H2O.
Lead Tellurite, 3PbTeO3.2H2O.
Magnesium Tellurite, 5MgTeO3.9H2O and 10MgTeO3.9H2O.
Manganous Tellurite.—This salt is readily oxidised by the air at ordinary temperatures to the manganic state.
Nickel Tellurite, NiTeO3.2H2O.
Potassium Tellurite, K2TeO3.3H2O; Potassium Ditellurite; Potassium Tetratellurite, K2Te4O9.4H2O.
Silver Tellurite, obtainable in several varieties, differing in colour.
Sodium Tellurite, Na2TeO3.5H2O; Sodium Ditellurite; Sodium Tetratellurite, Na2Te4O9.4H2O.
The ammonium salt could not be isolated. A copper ammonium tellurite of composition TeO2 = 83.84, CuO = 4.63, NH3 = 5.22, H2O = 6.10 per cent, has been obtained.


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