Thermodynamics of the cell Pt vertical bar H-2(p)vertical bar HCl (m)vertical bar AgCl vertical bar Ag and primary medium effects upon HCl in (glycerol plus water) solvents

The electromotive force (e.m.f.) E of the cell Pt \H-2(p)\ HCl(m) in Z \ Ag Cl \ Ag in {glycerol (G) + water (W)} solvents, Z = (G + W), up to glycerol mass fraction w(G) = 0.7 has been measured within the temperature range fr om 273.15 K to 313.15 K at HCl molalities up to 0.1 mol/kg(-1). On this bas is, the standard molar e.m.f. E-m(o) values pertaining to such solvent mixt ures have been obtained, and have been combined with sparse literature data for optimization. At glycerol mass fractions up to w(G)approximate to0.5, at constant temperature, E-m(o) shows a linear dependence on the glycerol m ole fraction X-G and, in parallel, E-c(o) (on the amount-of-substance conce ntration scale) shows linear dependence on the glycerol volume fraction phi (G). The primary medium effect upon HCl, defined as the difference (E-c(o) )w - (E-c(o))Z, has been considered as a function of the water volume fract ion phi (W) in terms of Feakins and French's theory: this would lead to a p rimary hydration number n(hydr) = 2.4 for HCl, in good agreement with previ ous results obtained with solvents other than (glycerol + water). In this c onnection, some basic methodological aspects are discussed. Ancillary value s of the densities rho (Z) of the relevant solvent mixtures, which were hit herto unavailable and are necessary for the data processing leading to E-m( o), have also been measured. (C) 2001 Academic Press.