Catalytic influence of Cl(-), Br(-), I(-) and SCN(-) on the cyclic voltammetric behaviour of Sb(III).
The electrocatalysis of the reduction of Sb(III) ions at a mercury electrode by Cl(-), Br(-), I(-) and SCN(-) ions and its dependence on the hydrogen-ion concentration has been studied in 4M (H, Na)ClO(4) solutions by cyclic voltammetry. The electrocatalytic capacity increases considerably in the order Cl(-) < SCN(-) < Br(-) < I(-) and a ligand-bridging mechanism is probably involved. Increasing the acidity at constant bridging-ligand concentration enhances the reaction rate. This can be explained by assuming that the influence of the hydrogen-ion concentration on the bridged activated complex is the same as on the Sb(III) complexes present in the bulk of the solution. From an analytical point of view it is important that the reduction of Sb(III) ions at a mercury electrode proceeds reversibly in the presence of Cl(-), Br(-), I(-) or SCN(-) ions.
Verplaetse
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Laboratory of Analytical Chemistry, State University Ghent, J. Plateaustraat 22, 9000 Ghent, Belgium.
Kiekens
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Temmerman
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Verbeek
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