Viscosity of Na2SO4 and MgSO4 solutions in ethanol–water mixtures at 15, 25 and 35 °C

Abstract

The viscosities of the associated electrolytes Na₂SO₄ and MgSO₄ have been measured in the following water-rich mixtures of ethanol and water: 0, 5, 10, 15, 20, 25 and 30 wt% ethanol at 15, 25 and 35 °C, and the Jones–Dole equation has been found to be in good agreement with experiments in the concentration range studied: 10^–3 < c/mol dm^–3 < 5 × 10^–2. From conductance measurements the association constants in these systems at 25 °C were calculated, and the degrees of association and the B_ion and B_ion-pair coefficients were obtained. The viscosity decreases through ion-pair formation in the Na₂SO₄ solutions and it is a constant factor in the MgSO₄ solutions. The ion–solvent interaction increases in the MgSO₄ and decreases in Na₂SO₄ as the permittivity of the medium decreases. The B_Mg²⁺ coefficients suggest that these ions are controlling the viscosity of the solutions to a greater degree than was expected.