Washburn numbers. Part 3.—Alkali-metal chlorides in the DMSO+water system; comparison with hydrochloric acid; “structural” effects

Abstract

Washburn numbers for alkali-metal chlorides have been measured in the range 0–40 %(w/w) DMSO (x₂= 0–0.094) and are compared with literature values for H⁺Cl^–. There is evidence for significant incorporation of DMSO into near-neighbour shells of H⁺ and Li⁺; by making certain assumptions it is concluded that these ions, and Cl^–, are preferentially solvated DMSO.

The Washburn numbers of H⁺Cl, Li⁺Cl^– and K⁺Cl^– show maxima when plotted against x₂. Possible explanations of this behaviour, which is paralleled by that of the Walden products, are discussed in detail, and it is concluded that it arises mainly from shifts in the preferential rather than the total solvation of the ions. The maxima in w⁰_w are evidence for the retention of water-like structure in the region studied, but not necessarily for its enhancement.