The recovery of iridium from laboratory residues

Abstract

A reproducible procedure is given for recovering iridium from laboratory residues containing base metals, silver and strong complexing agents. The residues are ignited, evaporated to dryness several times with concentrated hydrochloric acid, washed with 6 N nitric acid to remove silver and base metals, reignited, and converted to sodium hexachloroiridate(IV) by heating at 625 °C for 2 h with sodium chloride in a stream of chlorine. The cooled melt is dissolved in water, boiled with aqua regia and the iridium precipitated in yields above 80% as ammonium hexachloroiridate(IV) with ammonium chloride solution.