Thermodynamic studies of hydrogen iodide in dioxane-water mixtures from electromotive force measurements

The standard potentials of the silver-silver iodide electrode were measured in 10,20,30 and 40% (w/w) dioxane-water mixtures at 15,25,35 and 45°C. These values have been used to determine the thermodynamic quantities ΔG_t°, ΔS_t°, ΔH_t° for the transfer of H⁺I^? from water to various dioxane-water mixtures. The ionic ΔG_t° values for H⁺, Cl^?, Br^? and I^? are determined using Feakins method. The chemical and electrical contributions of ΔG_t° are also calculated using the method proposed by Roy and co-workers. The significance of these thermodynamic functions is discussed in relation to the acid—base character of the solvents.