It is an indigo-blue powder, soluble in hydrochloric acid, but insoluble in dilute nitric and sulphuric acids.
Iridium tetrachloride, IrC1 41 is obtained by dissolving the finely divided metal in aqua regia; by dissolving the hydroxide in hydrochloric acid; and by digesting the hydrated sesquichloride with nitric acid.
It decomposes steam at a red heat, and slowly dissolves in dilute hydrochloric and sulphuric acids, but more readily in nitric acid.
It is somewhat readily oxidized; nitric acid gives carbonic and oxalic acids, and chromic acid, carbonic and acetic acids.
Heated with sulphuric acid and with nitric acid it is oxidized to boric acid, whilst on fusion with alkaline carbonates and hydroxides it gives a borate of the alkali metal.