Viscosity measurements of some tetrabutylammonium, copper(I), silver(I) and thallium(I) salts in acetonitrile–pyridine mixtures at 15, 25 and 35 °C

Abstract

Viscosities and molar conductances of Bu₄NBPh₄, Bu₄NClO₄, CuClO₄·4AN, AgClO₄ and TlClO₄ have been measured in the concentration ranges (30–425)× 10^–4 mol dm^–3 and (1–35)× 10^–4 mol dm^–3, respectively in acetonitrile–pyridine (AN–Py) mixtures containing 0, 10, 20, 40, 60, 80, 90 and 100 mol% AN at 15, 25 and 35 °C. The viscosity data have been analysed using the Jones–Dole equation in the form: η/η°= 1 +AC^1/2+BC for unassociated electrolytes and in the form: η/η°= 1+A(Cα)^1/2+BCα+B′(1 –α)C for the associated electrolytes. The A-coefficients of the Jones–Dole equation are positive and in reasonably good agreement with the limiting theoretical values (Aη) calculated at all the three temperatures using Falkenhagen–Vernon equation. The B-coefficients of the electrolytes are also positive and large in all cases and show a significant decrease with increase in temperature. The ionic B₊ and B_– coefficients have been evaluated from the B-coefficients of the electrolytes using a method reported by Gill and Sharma. The derived viscosity results show preferential solvation of Cu⁺, Ag⁺ and Tl⁺ by Py in AN–Py mixtures at all the temperatures studied.