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[References: 37 tit.]

The process of electrooxidation of a lead-rhodium binary deposit on a graphite electrode has been studied. The anodic voltammetric curves show the peak of electrooxidation of lead (− 0.52 V), the peak of electrooxidation of hydrogen sorbed on the rhodium (+ 0.2 V), and additional peaks at potentials − 0.42 and − 0.30 V, the nature of which has been investigated. Using the theory of regular solutions, the changes in the equilibrium potentials of lead in lead-rhodium alloys in comparison with the equilibrium potential of lead were calculated. The data obtained showed that the anodic peak at potential − 0.42 V can be due to the selective electrooxidation of lead from the Pb4Rh intermetallic compound (IMC), and the peak at potential − 0.30 V can be due to the selective electrooxidation of lead from the Pb2Rh IMC. The presence of a stable phase structure is confirmed by data obtained by examining the surface of a graphite electrode with a binary lead-rhodium deposit using scanning electron microscopy (SEM). For analytical purposes, it is convenient to use the peak of selective lead electrooxidation from the intermetallic Pb2Rh compound observed on the voltammetric curve at potential − 0.30 V. The current of this peak is proportional to the concentration of rhodium(III) ions in the solution.