The standard potentials of silver–silver halide electrodes and ion solvation in dimethyl sulphoxide–water mixtures at 25 °C

Standard e.m.f.s of the cells H2|HX|AgX–Ag (X = Cl, Br, or I) in 10, 60, 70, and 80%(w/w) dimethyl sulphoxide–water mixtures are reported. These, together with values for mixtures of other compositions determined earlier, were used to calculate the molar free energies of transfer of the halogen acids from water to the mixed solvents. Single-ion values were derived therefrom by use of the extrathermodynamic assumptions of Feakins et al. and discussed in terms of ion solvation. It is shown that the solvophilicity of the ions is largely determined by their acid–base' interactions with the solvent molecules. The structural features of the solvents are briefly discussed.