Effect of temperature on the partial molar volumes of some divalent transition metal sulphates and magnesium sulphate in the water-rich region of aqueous mixtures of ethylene glycol

Abstract

Partial molar volumes of some divalent transition metal sulphates, viz. manganese sulphate, cobalt sulphate, nickel sulphate, copper sulphate, zinc sulphate and magnesium sulphate, have been determined (in the concentration range 0.005–0.100 mol kg − 1 ) in water and aqueous mixtures of ethylene glycol (EG) (5%, 10%, 15%, 20% and 25% by weight of EG) from solution density measurements at 303.15 K, in water and in 5% (w/w) EG + water at five different temperatures. The data have been analysed using the Masson equation and the obtained parameters interpreted in terms of ion–ion and ion–solvent interactions. The partial molar volumes vary with temperature as a power series of temperature. Structure making/breaking characters of the electrolytes have been inferred from the sign of [∂ 2 ϕ v 0/∂ T 2] p, i.e. second derivative of partial molar volume with respect to temperature at constant pressure. All the electrolytes have been found to act as structure makers/promoters in water as well as in aqueous mixtures of ethylene glycol.