EFFECT OF CHLORIDE ON THE KINETICS OF ELECTROÖXIDATION OF CHROMIUM(II) IN ACIDIC PERCHLORATE MEDIUM1

Abstract

The effect of chloride on the kinetics of the electrooxidation of chromium(II) in acidic 1 M sodium perchlorate solution was studied by the potentiostatic technique at the hanging mercury drop electrode. A convenient method of in sittu generation of chromium(II) for electrode kinetic studies was devised by a simple modification of the direct potentiostatic technique. At constant applied potential, the oxidation of chromium(II) is enhanced by chloride, the reaction following two parallel paths. The first is independent of chloride, yielding hexaquachromium(III), and the second is first order ia chloride at chloride concentrations up to 50 millimolar, yielding chloropentaaquachromium(III). The ability of the halides to enhance the reaction increases from fluoride to chloride to iodide, indicating that tendency of the halides toward specific adsorption at the electrode surface determines their relative efficiencies in enhancing the reaction. (auth)