Thermodynamics of NaCl in aqueous ethylene glycol, acetonitrile, and 1,4-dioxane mixtures from Emf measurements at 25°C

The emf. of the amalgam cell {NaxHg1-x|NaCl(m)|AgCl|Ag} has been measured at 25° as a function of the mole fraction x of Na in amalgams and of the molality m of NaCl in (ethylene glycol + water), (acetonitrile + water), and (1,4-dioxane + water) mixed solvents, contg. up to 0.8 mass fraction of the org. component, with relative permittivities ε ≥ 27. The relevant std. molal electromotive forces Em0 have been detd., together with the mean molal activity coeff. γ± of NaCl as a function of its molality. In the case of (ethylene glycol + water) mixts., a linear dependence of Em0 the mass fraction of ethylene glycol is obsd., which is quite unusual. The Debye-Huckel equation is applicable successfully over the whole range of molalities explored, which extends to the vicinity of the soly. limit of NaCl in each solvent. The dependence of the std. emf. on the logarithm of the vol. fraction of water in the aq.-org. solvent mixts. have been analyzed in terms of Feakins and French's theory, leading to a primary hydration no. 7.2 for NaCl, in good agreement with previous results employing different methods.