Acetone +NN-dimethylformamide solvent system. Part 3.—Viscosity measurements of some electrolytes in acetone, NN-dimethylformamide and acetone +NN-dimethylformamide mixtures at 25 °C

Abstract

Viscosities of Bu₄NBPh₄, Bu₄NNO₃, Bu₄NI, NaBPh₄, NaClO₄, KClO₄, KI and AgNO₃ have been measured in acetone (Ac), NN-dimethylformamide (DMF) and in acetone +NN-dimethylformamide (Ac + DMF) mixtures in the concentration range (25–575)× 10^–4 mol dm^–3 at 25 °C. The viscosity data in all those cases where no ion association of the electrolytes occurs have been analysed using the Jones–Dole equation in the form: η/η₀= 1 +AC^1/2+BC; where ion association occurs the following equation was used: η/η₀= 1 +A(Cα)^1/2+BCα+B′(1 –α)C. The A coefficients are positive in almost all cases and are in reasonable agreement with the limiting theoretical values calculated from Falkenhagen–Vernon equation. The B coefficients are also positive and large in all cases.

A new approach has been proposed to resolve B coefficients into the contributions of individual ions and the ionic B₊ and B_– coefficients have been obtained using this approach. The B₊ and B_– coefficients have been interpreted in terms of ion–solvent interaction. The conclusions drawn from viscosity measurements are in agreement with those obtained from conductance measurements.