Alkaline aqueous solutions of potassium borohydride have been found to give rise to a reproducible static potential at platinum electrodes. The reaction determining this potential seem to be a two-electron partial hydrogen ionization process. On anodic polarization, further ionization of hydrogen occurs accompanied by hydrolysis and hydrogen evolution, and an activation overpotential is apparent which has been precisely measured under a variety of conditions. The results; which show some unusual features, have been interpreted according to current concepts of electrode kinetics. Combined stoichiometric and kinetic data suggest a reaction mechanism in which the ratedetermining step is the partial hydrogen ionization of the first hydrolysis product of the borohydride ion. At electrodes which are inactive for the ionization of hydrogen, the borohydride ion is not readily oxidized until a potential approaching that of oxygen evolution is reached.
Alkaline solutions of sodium sulphide containing dissolved sulphur have been found to give rise to reproducible equilibrium potentials at inert electrodes. On anodic polarization of such electrodes, oxidation of the sulphide ion to polysulphide occurs and an activation overpotential is apparent which has been precisely measured under a variety of conditions. The results have been interpreted in terms of current concepts of electrode kinetics, and a hypothesis of the mechanism of the anodic reaction is tentatively proposed in which the rate-determining step involves the transfer of a sulphur atom from an adsorbed polysulphide ion at the electrode to a polysulphide ion in solution.
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