The cosolvent effect on the transport parameters of HCl in aqueous + organic solvent mixtures

The electromotive forces EA of concentration cells with transference Ag\AgCl\HCl(m(2,var)), (S + H2O)\\HCl(M-1,M-fixed), (S + H2O)\AgCl\Ag, where m(1,fixed) and M-2,M-var denote electrolyte molalities (fixed and variable, respectively), have been measured at T = 298.15 K in a wide range of aqueous organic solvents (S + H2O) with both protic (methanol, ethanol, propanol, ethylene glycol, and glycerol) and aprotic cosolvents (propylene carbonate, acetonitrile, and 1,4-dioxane) of low to high permittivities, allowing the determination of infinite dilution ionic transference numbers for HCl in such solvents. Appropriate combination of the latter with limiting molar conductivity data, determined in the same media, yielded the limiting ionic mobilities. The results provide an insight on the effect of the organic cosolvents on relative and absolute transport properties of HCl. They are compared with results obtained by our group for "viscous-motion" alkali halides MeCl, discussed in terms of dielectric friction parameters. For the limiting case of pure water, the abundant transference cell data available up to very high HCl concentrations have now been reassessed along our recently improved interpretative scheme.