REDOX EQUILIBRIA IN THE IN(III)-IN(I)-IN SYSTEM IN AQUEOUS KBR SOLUTIONS .1. POTENTIOMETRIC AND COULOMETRIC STUDY

The reproportionation of In(I) ions in acidic potassium bromide solutions was studied by means of the coulometric and potentiometric method. The formal potentials of the In(III)/In(I), In(III)/In and In(I)/In redox couples as well as the equilibrium constants of the reaction In(III) +2 In = 3 In(I) were determined at a background electrolyte concentration ranging from 1 to 4 mol dm-3. Based on the experimental results, a scheme of the reproportionation reaction was proposed with regard to the participation of bromide ions. In addition, the diffusion coefficient of In(I) ions was determined using the chronopotentiometric technique.