Notes on the Preparation and Analysis of Halogenide-Free Rhodium(III) Perchlorate (Sulfate) Solutions

Abstract : A method is described for the preparation of halogenide-free rhodium(III) perchlorate (sulfate) solutions. As starting material, rhodium chloride or rhodium bromide can be used. The halogenide was removed by means of ozone, which oxidizes "free" (not complex-bound) halogenide to halogen and Rh(III) to RH(V): O3 + 2X(-) + 2H(+) yields Rh(V) + O2 + H2O (1) X = Cl or Br; Rh(III) + O3 + 2H(+) yields Rh(V) + O2 + H2O (2). The Rh(V) produced, being a strong oxidizing agent, also reacts with the halogenide according to Rh(V) + 2X(-) yields Rh(III) + X2 (3). Methods for the detection of halogenide-ions in rhodium solutions are given.