Kinetics of oxidation and of catalytic decomposition of hexacyanoferrate(II) ion

Abstract

In the absence of light, oxygen oxidizes the hexacyanoferrate(II) ion to hexacyanoferrate(III) ion only in acid solutions. The first-order rate constants of oxidation are proportional to the sum of the concentrations of mono- and di-hydrogen hexacyanoferrate(II) ions, which suggests the involvement of these ions in the oxidation process. Thermal decomposition of hexacyanoferrate(II) ion in aqueous and mixed solvents is strongly catalysed by the addition of small amounts of mercury(II) ions. Kinetic measurements suggest that mercury(II) ions form ion-pairs with hexacyanoferrate(II) ions, and that the rate-determining step is the attack of the mercury(II) ion from the solvation shell on the cyano-group.