The residue so obtained is then powdered and ignited with barium nitrate, which converts the iridium into its oxide and the osmium into barium osmiate.
They also combine with nitrosyl bromide and chloride, and with many metallic haloid salts (platinum bichloride, iridium chloride), with mercury salts (see K.
Potassium iridium sesquichloride, K 3 IrC1 6.3H 2 O, is obtained by passing sulphur dioxide into a suspension of potassium chloriridate in water until all dissolves, and then adding potassium carbonate to the solution (C. Claus, Jour.
Glass stills heated by a sand bath are sometimes employed in the final distillation of sulphuric acid; platinum, and an alloy of platinum and iridium with a lining of gold rolled on (a discovery due to Heraeus), are used for the same purpose.
Nitric acid is without action on gold, platinum, iridium and rhodium.
Iridium sesquioxide, Ir 2 0 3, is obtained when potassium iridium chloride is heated with sodium or potassium carbonates, in a stream of carbon dioxide.
The disulphide, IrS2, is formed when powdered iridium is heated with sulphur and an alkaline carbonate.
It may be obtained in the spongy form by igniting iridium ammonium chloride, and this variety of the metal readily oxidizes when heated in air.
When Q, Iridium pivct.
The iridium is then precipitated from the solution (as oxide) by the addition of baryta, dissolved in aqua regia, and precipitated as iridium ammonium chloride by the addition of ammonium chloride.