Extraction of iridium with tetraphenylarsonium chloride and its flotation—spectrophotometric determination with rhodamine 6g

A sensitive flotation—spectrophotometric method, based on the ion-associate formed by the anionic chloride and chlorostannate(II) complex of iridium with the basic dye rhodamine 6G (R6G) is described. A sparingly soluble compound precipitates when the aqueous phase is shaken with di-isopropyl ether. The separated and washed compound is then dissolved in acetone. The molar absorptivity is 3.6 × 10⁵ l mol^-1 cm^-1 at 530 nm. Beer's law is obeyed. The component ratios in the isolated compound were determined, and the formula (R6G⁺)₃IrCl₂(SnCl₃)^3-₄] · (R6G⁺)(SnCl^-₃)] is proposed for the adduct. The effects of other noble metals were examined. The interferences of rhodium and platinum with the determination of iridium in the proposed method can be greatly decreased by a preliminary extractive separation of iridium into chloroform as a tetraphenylarsonium hexachloroiridate(IV) complex. Optimum conditions for the iridium extraction are reported.