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Exchange currents have been measured of some liquid and solid metal electrodes (Cd, Zn, Pb, Bi, Ag, Ni, Pt) and one redox system (V~+/V ~*) in a KC1-LiC1 eutectic melt at 450~ Measurements over a hundredfold concentration range permitted calculation of the heterogeneous rate constant and of the transfer coefficient. Two relaxation methods were used: the double pulse method as developed by Gerischer and Krause and the voltage step method as described by Vielstich and Delahay. In cases where both methods were applied independently to the same system the results were in good agreement. The purity of the eutectic melt was improved considerably by filtration and by displacement of heavy metal ion impurities with metallic magnesium. The evaluation of voltage step measurements was revised by allowing for the effect of the finite charging time of the double layer. Agreement was not found with the theory of the double pulse method given by Matsuda, Oka, and Delahay, perhaps because of some additional process, other than diffusion, taking place in a period of time comparable to the duration of the first pulse. On the basis of the reaction of platinum with cadmium at 450~ it is possible to account for the observations made earlier in this laboratory by C. H. Liu and tI. C. Gaur on the emf and polarization behavior of cadmium-plated platinum electrodes.

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The authors are grateful to C.S.I.R.

The polarographic reduction potentials and the half-lives of the initial radical anion reduction products have been measured for a representative group of ,/3-unsaturated ketones. In dipolar aprotic media (DMF, HMP) the radical anion 16 derived from 2,2,6,6-tetramethyl-?ra«i-4-hepten-3-one (11) has a sufficiently long halflife (ca. 10 min) to permit measurement of its properties. The lifetime of this radical anion 16 is markedly lowered by the presence of proton donors, lithium cation, or oxygen in the reaction medium. In the presence of proton donors or metal cations, this radical anion 16 is rapidly converted to a racemic dihydrodimer 24. Evidence is presented for two geometrically isomeric radical anions 17 and 16 being formed by reduction of the cis ( 14)-and trans (ll)-enones. However, one of the isomeric anion radicals is rapidly converted to the other more stable isomer believed to be 16. Epr measurements have demonstrated the occurrence of electron exchange between the radical 14