THE CHEMISTRY OF IRIDIUM IN BASIC AQUEOUS SOLUTION: A POLAROGRAPHIC STUDY

Abstract

The polarographic behavior of iridium(IV) has been studied in basic solutions at 25 °C at an ionic strength maintained with sodium chloride at 0.50 M. Between pH 11.3 and 13.0, a reversible, diffusion-controlled, one Faraday per mole reduction wave was obtained. The E1/2 was −0.60 V versus a saturated calomel reference electrode at pH 12.0; a shift of −57 mV per pH unit indicated that one hydrogen ion is involved in the reduction. With basic solutions of iridium(III), the corresponding oxidation wave was obtained, but the metal was easily air oxidized. The basic iridium(IV) species gave an absorption peak at 313 mμ. The rate of formation of the basic iridium(III) complex from an acid iridium(III) solution was found to be more rapid than that of the basic iridium(IV) complex from an acid iridium(IV) solution. The reaction of iridium (IV) with ethylenediaminetetracetate was also studied.