Transference number measurements of silver nitrate in pure and mixed solvents using the electromotive force method
Abstract
Transference numbers of NO–3(tNO–3) and Ag+(tAg+) 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.