Thermodynamics of the cell Pt | H2(p)| HCl (m)| AgCl| Ag and primary medium effects upon HCl in (glycerol + water) solvents

The electromotive force (e.m.f.)E of the cellPt|H₂(p)|HCl(m) in Z|AgCl|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 from 273.15 K to 313.15 K at HCl molalities up to 0.1mol · kg ^− 1. On this basis, the standard molar e.m.f. E_m ^∘ values pertaining to such solvent mixtures have been obtained, and have been combined with sparse literature data for optimization. At glycerol mass fractions up tow_G ≈  0.5, at constant temperature,E_m ^∘  shows a linear dependence on the glycerol mole fractionx_G and, in parallel, E_c ^∘ (on the amount-of-substance concentration scale) shows linear dependence on the glycerol volume fractionϕ_G . The primary medium effect upon HCl, defined as the difference (E_c ^∘ )_W −  (E_c ^∘ )_Z, has been considered as a function of the water volume fraction ϕ_Win terms of Feakins and French’s theory: this would lead to a primary hydration number n(hydr)  =  2.4 for HCl, in good agreement with previous results obtained with solvents other than (glycerol  +  water). In this connection, some basic methodological aspects are discussed. Ancillary values of the densities ρ_Zof the relevant solvent mixtures, which were hitherto unavailable and are necessary for the data processing leading toE_m ^∘  , have also been measured.