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

Tellurium Tetra-iodide, TeI4






Tellurium Tetra-iodide, TeI4 may be prepared in a very pure state by heating together finely divided tellurium and excess of iodine and allowing the product to cool slowly. The excess of iodine may be removed by extracting with carbon tetrachloride.

The tellurium tetra-iodide may also be formed from the dioxide and concentrated hydriodic acid. Telluric acid gives a similar result. The resulting halide may separate as such or in needles of an additive compound, HI.TeI4.8H2O, which gives a residue of tetra-iodide when warmed to 50°- 60° C.

The tetra-iodide forms small, brilliant, black crystals, having a density of 5.05 at 15° C. When heated above 100° C. it dissociates into tellurium and iodine. When dissolved in excess of iodine it appears probable that part of the iodide is in a bimolecular condition. It is unattacked by moist air, but is slowly decomposed by cold water, and on warming, hydrolysis occurs with the formation of an oxy-iodide of uncertain composition; on boiling with water complete hydrolysis to hydrogen iodide is effected:

TeI4 + 3H2O = H2TeO3 + 4HI.

It is sparingly soluble in alcohol and acetone, insoluble in ether, chloroform and carbon disulphide. Alkalis and ammonia in aqueous solution readily dissolve it. It is also soluble in a solution of hydriodic acid.

Analogous with the tetrachloride and tetrabromide, additive compounds are formed by the tetra-iodide with the alkali iodides. The telluri-iodides, of the general formula X2TeI6, are black, crystalline substances, which, like the tellurichlorides and telluribromides, generally crystallise in the regular system when anhydrous. They are decomposed by water in the same way as the tetra-iodide, although they are soluble without decomposition in concentrated hydriodic acid. It has not been found possible to obtain the corresponding di-hydrogen tellurium hexa-iodide. By the interaction of tellurium tetra-iodide, iodine and hydriodic acid in a sealed tube, the only product is a substance having the composition TeI4.HI.8H2O.


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