Transference number measurements of silver nitrate in pure and mixed solvents using the electromotive force method

Abstract

Transference numbers of NO^–₃(t_NO^–3) and Ag⁺(t_Ag⁺) in AgNO₃ have been measured at several concentrations in the range 0.01538–0.2000 mol dm^–3 in N,N-dimethylacetamide (DMA), pyridine (Py) and in acetonitrile (AN)–DMA, AN–Py, AN–nitrobenzene (NB) and methanol (MeOH)–N,N-dimethylformamide (DMF) mixtures containing 20, 40, 60 and 80 mol % AN or MeOH at 25 °C usiong the e.m.f. method. The transference numbers show practically no concentration dependence on AgNO₃ in DMA and in AN–DMA mixtures but a significant concentration dependence in all other cases. The limiting transference numbers of Ag⁺(t^°_Ag+) in the former cases have been obtained by calculating the average of practically constant values of transference numbers of Ag⁺ at different AgNO₃ concentrations while in all other cases by using the Longsworth method in the form suggested by Kay and Dye. The t^°_Ag+ values in various solvent mixtures have been found to vary significantly with the solvent composition. The λ^°_Ag+ and λ^°_NO3– values have been obtained in all the solvent systems studied by combining Λ₀ values of AgNO₃ with the present t^°_Ag+ values. The plots of the Walden product for Ag⁺ and NO^–₃ as a function of solvent composition show preferential solvation of Ag⁺ and NO^–₃ by specific solvents in these mixed solvents.