Studies in ion solvation in non-aqueous solvents and their aqueous mixtures. Part 19.—Free energies of transfer of alkali metal chlorides from water to DMSO + water mixtures up to 40%(w/w) DMSO, of sodium chloride to 60%(w/w) DMSO and of potassium bromide and iodide to 10%(w/w) DMSO. Comparison with silver chloride

Abstract

Free energies of transfer of the alkali metal chlorides from water to dimethylsulphoxide (DMSO)+ water mixtures up to 40% DMSO, of Na⁺Cl^– to 60% DMSO, and of K⁺Br^– and K⁺I^– to the 10% mixture are reported. Agreement with the glass-electrode measurements of Smits, Massart, Juillard and Morel is good, but is less satisfactory with the amalgam-electrode measurements of Das and Kundu. The relatively high solubility of the silver halides in the mixtures necessitates changes in the usual experimental technique. “Soft–soft” interactions are discussed. The presence of DMSO, rather than a “hard” co-solvent like methanol, has no obvious effect on the behaviour of the larger alkali metal ions, but has a marked effect on the behaviour of Ag⁺, no doubt because of π-bonding effects.