The determination of iridium and ruthenium in rhodium sponge by solvent extraction followed by atomic-absorption spectrophotometry

Abstract

A method is described for the determination of trace amounts of iridium and ruthenium in rhodium sponge. The sponge is dissolved by treatment with concentrated hydrochloric acid and sodium chlorate in a sealed glass tube at 250 °C. Chloro-complexes of rhodium and other noble metals are produced. From such a solution, 2 M in hydrochloric acid, iridium and ruthenium are extracted into chloroform that is 1 per cent. m/V in methyltriphenylphosphonium chloride; rhodium is not extracted. The organic phase is evaporated to dryness and the residue dissolved in acetonitrile containing lithium perchlorate, which is the interference suppressant for the subsequent determination of iridium and ruthenium by atomic-absorption spectrophotometry.

Osmium can be determined in rhodium sponge in a similar manner if precautions are taken so as to prevent loss of osmium when the tube is opened. The results are in good agreement with those obtained by emission spectrography and the limits of detection for iridium and ruthenium in the sponge are 7 and 4·5 µg g^–1, respectively.