STUDIES OF UNUSUAL OXIDATION STATES OF TRANSITION METALS (Ⅰ)——KINETICS AND MECHANISM OF OXIDATION OF POTASSIUM THIOCYANATE BY DIPERIODATOARGENTATE(Ⅲ) ION IN ALKALINE MEDIUM

摘要

The kinetics of oxidation of potassium thiocyanate by diperiodatoargentate （Ⅲ） （DPA） ions was studied in aqueous alkaline medium ([OH-]=7.00×10-3—0.200 mol. dm-3) at a constant ionic strength (μ=0.30 mol. dm-3). It is found that the reaction order in DPA is unity. The dependence of the rate on [OH-] implies that there are two pathways through which the reaction proceeds. In each pathway, the order in NCS-is fractional and the kinetic data fit well in with Michaelis-Menten process. The influence of ligand on the reaction is examined and the reactive species are inferred. Two pathways of inner-sphere two-electrons transfer are believed to be involved in the oxidation. The rate equations are derived and all the equilibrium constants and rate constants are evaluated. Activation parameters of one pathway are determined.