Absolute electrode potentials in dimethyl sulphoxide-water mixtures and transfer free energies of individual ions

Abstract

The standard potentials of H 2|H +, M|M + (M = Li, Na, K, Rb and Cs) and Ag¦AgX (X = Cl, Br and I) electrodes in seven aqueous solutions of dimethyl sulphoxide (DMSO), containing up to 60 wt.% DMSO, have been determined from EMF measurements of cells of the type: Ag¦AgX¦MX ( m), S¦M(Hg)¦MX ( m), W¦AgX¦Ag, or a variant of it, at 25°C by our recently reported procedure. The interest, validity and general applicability of this procedure in both aqueous protic and aprotic solvents have been demonstrated. The radii of solvated cations and their solvation extent in these media have been calculated. The standard Gibbs free energies of transfer of halogen acids and alkali metal halides as well as their constituent individual ions from water to each of the DMSO-water mixtures have been also computed. The results are interpreted and discussed.