The steady-state velocities of an electrodic redox reaction have been determined on noble metals and some of their alloys. They are expressed in terms of the exchange current densities io. Correspondingly, measurements of io's as a function of temperature are recorded. The heats of activation at the reversible potential are independent of the properties of the substrate. However, log (reaction rate at the reversible potential) is linear with the work function of the substrate. Reactions in Cl-containing solutions have velocities greater than those in S04--solutions, and the ratio VCl-/VS04-_ depends upon the substrate in the order Pd>Au>Pt. The lack of dependence of the heat of activation upon the substrate is consistent with an electron transfer and not an atom-transfer model for the electrodic redox reactions. It is consistent with a weak interaction model. The dependence of the exchange current densities upon the substrate can be shown quantitatively to depend on the change of electrokinetic potential with the change of substratesolution PD (potential difference) which occurs by carrying out the same reaction at a series of interfaces at which the metal-solution PD's are different, while the reversible potentials are the same. The anion effects cannot be due to blocking or bridging. They may be due to change in the 'l'2-b potential arising from a differing contact adsorption of the anions.157 (1955).

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Evidences for the enhancement of the heterogeneous electron transfer rates of riboflavin in the presence of copper in aqueous medium with a glassy carbon electrode were investigated by cyclic voltammetry, chronocoulometry and differential anodic stripping pulse voltammetry. It was found that copper exhibits a multi-nuclear complex with riboflavin in aqueous KCl solution. The overall stability constant of the complex was calculated (logβ = 11.17), which is in a good agreement for the formation of a stable copper-riboflavin complex.