ELECTROCHEMISTRY OF [V(III)EDTA](-) IN ETHYLENE GLYCOL-WATER MIXTURES.1. THERMODYNAMIC AND TRANSPORT-PROPERTIES - SOLVATION OF THE REACTANT AND PRODUCT

The effect of the solvent composition for water-ethylene glycol (EG) m ixtures in the mole fraction range X(EG) = 0-1 on the diffusion coeffi cients and formal potentials of the lenediamine-N,N,N',N'-tetraacetato vanadate(III/II) redox reaction has been investigated at a mercury ele ctrode using convolution potential sweep voltammetry. It has been show n that the formal potential of the redox reaction, measured on the fer rocene/ferricinium scale, depends on the solvent composition. This dep endence has been characterized by a two-step solvent exchange mechanis m, which describes the solvation of the reactant and product. Distribu tion diagrams for the differently solvated species have been calculate d as a function of the mole fraction of EG. Preferential solvation of the more negatively charged vanadium(II) complex relative to the vanad ium(III) complex by water has been found. Acceptor numbers for the mix tures have been proposed.