IONIC PROPERTIES IN ACETONITRILE PLUS WATER MIXTURES AND DIMETHYLFORMAMIDE PLUS WATER MIXTURES

Emf measurements at 298 K are reported for Wagner-type galvanic cells with flowing liquid junctions in which one half-cell contains an aqueo us electrolyte solution and the other contains the same electrolyte in either acetonitrile (AN) + water mixtures or dimethylformamide (DMF) + water mixtures of varying composition. The electrolytes LiCl, NaCl a nd KCl have been studied in the AN + water system using Ag/AgCl electr odes, while LiCl, NaCl, KCl and NaBr have been studied in the DMF + wa ter system using flowing amalgam electrodes in each half-cell. The dat a have been combined with standard Gibbs energies of transfer data fro m the literature and conductance data, much of it reported here for th e first time, to obtain solvation potentials for the cells. Transport numbers for these electrolytes are also reported. The results show tha t DMF displaces water in the cation solvation sheath as the organic co ntent of the mixed solvent increases, whilst AN shows a similar but le ss marked effect.