A polarographic study of zinc-thiocyanate complexes in mixed solvents

Abstract

Complexes of zinc with thiocyanate were studied polarographically in aqueous mixtures of methanol, ethanol, dioxan and dimethyl formamide (dmf). The reduction, in most cases, was not reversible and the degree of irreversibility increased with the percentage composition of the mixed solvent as well as with the nature of the solvent in the order: alcohols <dioxan≅dmf. The ‘formal’ potentials for reduction, determined by amalgam polarography at different thiocyanate concentrations in each solvent mixture, were used to calculate the standard rate constant,k _z, and the transfer coefficient, α, for the reduction from the current-potential data. The stability constants of the complexes, also evaluated from the ‘formal’ potentials, varied linearly with the dielectric constant of the medium.