ELECTRODE PROCESSES OF THE EU(III) EU(II) SYSTEM IN ACETONE PLUS DIMETHYLFORMAMIDE MIXTURES/

The electrode reaction of the Eu(III)/Eu(II) system on a mercury elect rode in acetone + dimethylformamide mixtures was studied. Owing to a s maller change in the dielectric constant of the mixture of the two sol vents, in contrast to their mixture with water, neither of the compone nts accumulates in the double layer. On the contrary, because of their different basicity the europium cations are preferentially solvated b y dimethylformamide. Consequently, the dependence of the rate constant of the electrode reaction exhibits a marked minimum. The liquid junct ion potentials on the boundary of the mixture of organic solvents with water and the difference in energies of the transfer of Eu(III) and E u(II) from acetone to mixed solutions with dimethylformamide were also determined.