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

Abstract
An e.m.f. cell with transference similar in design to that developed by Rupert and recently used by Braun and Weingaertner has been fabricated. Using this cell transference numbers of NO3 (tNO3 ) in AgNO3 have been measured in the concentration range 0.01538–0.2000 mol dm–3 in water (H2O), acetonitrile (AN), methanol (MeOH), N,N-dimethylformamide (DMF), dimethyl sulphoxide (DMSO) and in AN–H2O, AN–MeOH, AN–DMF and AN–DMSO mixtures containing 20, 40, 60 and 80 mol% AN at 25 °C. The method is fast and reliable for transference-number measurements of AgNO3 in mixed non-aqueous solvents. The transference numbers of NO3 show practically no change with a change in AgNO3 concentration. The limiting transference numbers of NO3 (t°NO3 ) in various solvent systems have been obtained by calculating the average of the transference-number values of NO3 at different AgNO3 concentrations. The limiting transference numbers of NO3 in mixed solvents vary significantly with solvent composition. They show a maximum and a minimum in AN–H2O mixtures, a maximum in AN–MeOH mixtures and a continuous decrease in AN–DMF and AN–DMSO mixtures with an increase in [AN]. By combining t°NO3 values with the Λ0 values of AgNO3 in various solvent systems, λ°Ag + and λ°NO3 values have been calculated and their Walden product plotted as a function of solvent composition.

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