GB640577A - Improvements relating to the production of iridium - Google Patents

Abstract

Ammonium iridichloride is dissolved in water in the presence of a reducing agent to give a solution of ammonium iridochloride, and impurities are removed therefrom by fractional precipitation with ammonium or alkali metal (sodium) sulphide, hydrosulphide, polysulphide or thiosulphate. The precipitating agent, particularly ammonium sulphide, may conveniently constitute the reducing agent, although any other, e.g. sodium nitrite or ammonium or alkali formate, may be employed. After addition of the precipitating agent, the solution is heated to 70 DEG C. or above, and the precipitate then separated, this sequence being repeated many times when a very pure product is required. Examples describe an intermediate isolation of ammonium iridichloride by oxidation with nitric acid followed by the addition of ammonium chloride. If much platinum is present in the material to be purified it should be first removed by a known method. Ammonium iridichloride finally isolated as above may be reduced to metallic iridium (see Group II). A statement of the p art refers to the purification of H3(IrCl6) or Na3(IrCl6) by saturating an acidified solution thereof with hydrogen sulphide for a long period.ALSO:Iridium, which may be of spectrographic purity, is obtained by treating purified ammonium iridichloride (see Group III) with hydrogen in a covered silica tray at 700 DEG C, treating the cooled material with hydrofluoric acid to remove silica, then successively with dilute aqua regia and dilute nitric acid and finally igniting at 500 DEG -600 DEG C in a hydrogen atmosphere.