SOLVENT FRICTION MECHANISM OF AN ELEMENTARY CHARGE-TRANSFER STEP AND CATION-REGULATED PREEQUILIBRIUM FOR A PT FE(CN)(6)(4-/3-) ELECTRODE PROCESS/

The apparent standard rate constant, k(0), for a Pt/hexacyanoferrate(I I/III) electrode process, known to be strongly dependent on the nature and the concentration of supporting electrolyte (viz., of its cationi c component), is proven to also display a lateral dependence on the so lution viscosity (water/glucose mixtures, 0.24-2.0 M in KCl and LiCl). The viscosity performance is complementary to the catalytic effect of cations and seems to operate independently. The catalytic role of cat ions is discussed in terms of the preequilibrium concept, considering the influence of a double-layer potential on the effective concentrati on of reactant ions at the active site near the electrode, k(0) is inv ersely proportional to the solution viscosity, indicative of strong so lute/solvent and intersite electronic coupling, provided that the obse rved relationship is a manifestation of the solvent friction (''overda mped'') mechanism for an elementary electron-transfer step.