Iridium Disulphate, Ir(SO₄)₂

Iridium Disulphate, Ir(SO₄)₂, is obtained as a yellowish brown, amorphous mass on oxidising iridium sulphide with concentrated nitric acid.3 On gently warming, the reaction takes place with vigour, and, when complete, the nitrous fumes are expelled by repeated evaporation and re-solution in water.

It does not appear to yield double salts, and on warming with, concentrated sulphuric acid yields iridium sesquisulphate.

Two series of salts known as disulphates have been prepared, namely:

1. Green salts of the type M₂[Ir(SO₄)₂.OH.H₂O], and
2. Reddish brown salts of the type M₃[Ir(SO₄)₂.(OH)₂], where M stands for a monovalent metal.

Of these the former salts are usually acidic, whilst the latter are basic. They are readily converted, the one into the other, by addition of acid or base, as occasion requires. Several such salts have been prepared.