THE SEPARATION OF RHODIUM AND IRIDIUM BY ION EXCHANGE

Abstract

Separations of rhodium and iridium as chlorides by means of columns of the anion exchanger Amberlite IRA-400 are described. Iridium, is maintained in the quadripositive state by the addition of cerium(IV), the presence of which is necessary to counteract the reducing action of the resin. The marked difference in affinity toward the resin of Ir(IV) and Rh(III) makes the separation possible. Rhodium can easily be eluted from the resin by 2 M hydrochloric acid. Removal of all the iridium from the resin is accomplished in a Soxhlet extractor with 6 M hydrochloric acid. A number of less successful procedures for this separation are discussed.