Chemical elements
    Physical Properties
    Chemical Properties
    Atomic Weight
      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
      Tellurium Trioxide
      Telluric Acids
      Tellurium Disulphide
      Tellurium-Sulphur Sesquioxide
      Tellurium Sulphates
      Telluropentathionic Acid
      Tellurium Nitride
      Tellurium Nitrite
      Basic Tellurium Nitrate
      Carbon Sulphidotelluride
      Tellurium Dicyanide
    PDB 1el7-4fon

Tellurium Trioxide, TeO3

Tellurium Trioxide, TeO3, like so many of the tellurium compounds, was discovered by Berzelius. It is formed when telluric acid is heated a little above 360° C. Care is necessary, since overheating induces decomposition of the yellow trioxide into the colourless dioxide. Any dioxide that forms can be removed by treating with concentrated hydrochloric acid, in which the trioxide is only sparingly soluble.

Tellurium trioxide is an orange-yellow solid, of density 5.10 at the ordinary temperature. Its heat of formation per gram-molecular weight is 83.6 Calories, and according to Mixter the decomposition of the trioxide into the dioxide is an exothermic reaction. As might therefore be expected, this decomposition occurs readily and at such a temperature that the resulting dioxide is unfused.

The trioxide is insoluble in water, hot or cold, in nitric acid and in cold hydrochloric acid. Concentrated hydrochloric acid when heated attacks it with liberation of chlorine and formation of tellurium tetrachloride in the solution. The caustic alkalis only dissolve tellurium trioxide in hot concentrated solution, with formation of tellurates.

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