Chemical elements
  Iridium
    Isotopes
    Energy
    Production
    Application
    Physical Properties
    Chemical Properties
      Iridium Monochloride
      Iridium Dichloride
      Iridium Trichloride
      Potassium Chloriridite
      Sodium Chloriridite
      Ammonium Chloriridite
      Aquo Chloriridites
      Iridium Tetrachloride
      Potassium Chloriridate
      Sodium Chloriridate
      Ammonium Chloriridate
      Silver Chloriridate
      Thallium Chloriridate
      Iridium Tribromide
      Iridium Tetrabromide
      Potassium Bromiridate
      Sodium Bromiridate
      Ammonium Bromiridate
      Iridium Oxybromide
      Iridium Tri-iodide
      Potassium Iodiridite
      Iridium Tetra-iodide
      Potassium Iodiridate
      Iridium Monoxide
      Iridium Sesquioxide
      Iridium Dioxide
      Iridium Trioxide
      Iridium Monosulphide
      Iridium Sesquisulphide
      Iridium Disulphide
      Iridium Sesquisulphite
      Potassium Iridium Sulphite
      Iridium Sesquisulphate
      Potassium Iridium Alum
      Ammonium Iridium Alum
      Caesium Iridium Alum
      Rubidium Iridium Alum
      Iridium Disulphate
      Iridium Sesquiselenide
      Hydrogen Iridi-nitrite
      Potassium Iridi-nitrite
      Sodium Iridi-nitrite
      Ammonium Iridi-nitrite
      Hydrogen Iridicyanide
      Potassium Iridicyanide
      Barium Iridicyanide
    PDB 1c1k-4enb

Iridium Trichloride, IrCl3






Iridium Trichloride, IrCl3, is most conveniently prepared by heating the reduced metal - obtained by precipitation from an alkali chloriridate solution with magnesium - with sodium chloride in a current of chlorine at 600° to 620° C. The reaction is complete in a few minutes. The limits of stability of the salt under these conditions lie from below 100° C. up to 763° C. Above this latter temperature it dissociates in an atmosphere of chlorine into iridium dichloride and chlorine, and at still higher temperatures (773° C.) into the mono-chloride.

Iridium trichloride is also obtained by heating ammonium chloriridate or iridium tetrachloride in a current of chlorine at 440° C. and cooling the product in an atmosphere of carbon dioxide.

As obtained by the foregoing methods, iridium trichloride is a crystalline substance, olive-green in colour, of density 5.30. It is insoluble in water, alkalies, and acids; even concentrated sulphuric acid and aqua regia having no action upon it. It is appreciably volatile at 470° C.

An almost anhydrous salt is obtained by heating the yellow powder, produced by the action of sulphuric acid upon alkali chloriridites, in hydrogen chloride at temperatures up to 500° C. The colour remains essentially the same, and the composition of the product approaches very closely to that of iridium trichloride, with small quantities of hydrochloric acid and water, the formula being IrCl3.mHCl.nH2O, where m and n, however, are but small fractions of unity.

The product is different from ordinary iridium trichloride, however, in that it is deliquescent and soluble in water. On concentrating the solution and drying the product at 100° C. a sesquihydrate is obtained, 2IrCl3.3H2O. This dissolves in water, yielding a greenish yellow solution. Silver nitrate gives, with this solution, a precipitate, which upon drying at 110° C. has the composition IrCl3.AgOH.

The salt described in earlier literature as the tetrahydrate, IrCl3.4H2O, appears to be an indefinite mixture of the trichloride with water and hydrogen chloride, as represented by the formula IrCl3.mHCl.nH2O, where m is less than unity.


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