Ion solvation and structural effects on the transport of water in aqueous organic solvents. Glycerol + water + hydrochloric acid at 25°C

Abstract

The molar transference number or Washburn number of water, t_w has been determined in glycerol + water mixtures containing up to 50%(w/w) glycerol by an e.m.f. method using hydrochloric acid as electrolyte. t_w is the number of moles of water transported by the electrolyte per faraday towards the cathode in an electrolysis, relative to the organic component. The plot of t_w against solvent compo sition passes through a maximum at 10–30%(w/w) glycerol and a small inflexion at 30–50%(w/w)glycerol.

These features do not stem from the variations in transport numbers of the ions with solvent composition. Rather, they arise from the effects of solvent structure and “acid-base” interactions on the relative solvation of the ions by the two solvent components.