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 Sesquioxide, Ir2O3






Iridium Sesquioxide, Ir2O3, is obtained by igniting iridium sulphite, or by heating an alkali chloriridate with twice its weight of carbonate. The product is washed with hot water, and the colloidal residue treated with a solution of ammonium chloride to effect its coagulation, and finally with nitric acid and dried, the acid serving to remove the last traces of alkali.

In an impure form iridium sesquioxide is obtained by mixing hot solutions of potassium hydroxide and sodium chloriridite in an atmosphere of carbon dioxide. The solution is evaporated to dryness, and the residue heated to redness in a current of carbon dioxide. Further purification is effected by boiling first with sodium hydroxide solution and then with sulphuric acid.

When heated above 400° C. iridium sesquioxide decomposes, yielding metallic iridium and its dioxide, a little oxygen being likewise liberated. It dissolves in hydrochloric acid, yielding a colloidal solution.


Hydrated Iridium Sesquioxide

Hydrated Iridium Sesquioxide, Ir2O3.5H2O, is obtained as an olive- green precipitate on addition of the requisite quantity of potassium hydroxide solution to one of chloriridite. If excess of potash is taken no precipitate appears, since the sesquioxide dissolves as rapidly as formed, yielding an olive-green solution, from which, however, it is precipitated on addition of acid.

The precipitated oxide readily oxidises in air. It dissolves in acids to a yellowish green solution. The alkaline solutions readily oxidise on boiling in air or on addition of hydrogen peroxide, the dioxide being precipitated (vide infra). Boiling them with alcohol causes reduction to iridium black.
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