Partial molar volumes of oxalic acid and its salts in water-rich binary aqueous mixtures of methanol

Abstract

Partial molar volumes of oxalic acid and its salts, viz., ammonium oxalate, sodium oxalate and potassium oxalate, have been determined in different compositions of water-rich binary aqueous mixtures of methanol (3, 6, 9, 12, and 15 wt. percent of methanol) from solution density measurements at 298.15 K and in 3% (<i>w/w</i>) methanol + water at different temperatures. The data have been analysed by using Masson equation and the obtained parameters have been interpreted in terms of ion-solvent and ion-ion interactions. The partial molar volumes vary with temperature as a power series of temperature. Structure making/breaking capacities of the electrolytes have been inferred from the sign of ([∂²φ⁰_v / ∂T²)_p, i.e. the second derivative of partial molar volume with respect to temperature at constant pressure. Oxalic acid and its salts act as structure breakers in binary aqueous mixtures of methanol.