EFFECT OF MULTICHARGED CATIONS ON THE ELECTROREDUCTION OF ANIONS

According to the slow discharge theory, small additions of multicharge d cations (Ca2+, La3+, Th4+, etc.) accelerate the charge-transfer step during the electroreduction of anions of K3Fe(CN)6, K2S2O8, and Na2S4 O6 salts. However, the acceleration effect decreases at high cathodic potentials of a mercury electrode, and this contradicts the conclusion s of this theory in combination with the Gouy-Chapman-Grahame model of the double layer. It was shown that the observed results can be expla ined within the framework of the slow discharge theory and in combinat ion with the diffuse-layer model. According to this model, because of their smaller Stokes radius, single-charged cations K+ or Na+ of the s alt, in which the anion is being reduced, approach die metal surface m ore closely than the hydrated multicharged cations.