Ammonium Iridium Alum, (NH₄)₂SO₄.Ir₂(SO₄)₃

Ammonium Iridium Alum, (NH₄)₂SO₄.Ir₂(SO₄)₃.24H₂O, prepared in a similar manner to the preceding salt, crystallises in yellowish red octahedra, which melt at 105° to 106° C., yielding a reddish violet liquid. On heating still further the combined water is gradually expelled, whilst at red heat metallic iridium is obtained as residue.