A study on partial molar volumes of oxalic acid and its salts in binary aqueous mixtures of tetrahydrofuran at various temperatures

Partial molar volumes of oxalic acid and its salts, viz. ammonium oxalate, sodium oxalate and potassium oxalate, have been determined in binary aqueous mixtures of tetrahydrofuran (THF) [5, 10, 15 and 20 wt.% of THF] at 298.15 K, and in 5% (w/w) THF + water at five equidistant temperatures. The data have been evaluated using the Masson equation and the obtained parameters have been interpreted in terms of solute-solute and solute-solvent interactions. The partial molar volumes vary with temperature as a power series of temperature. Structure making/breaking capacities of oxalic acid and its salts have been inferred from the sign of [∂2ϕv0/∂T2]p, i.e. the second derivative of partial molar volume with respect to temperature at constant pressure. The oxalic acid and its salts act as structure breakers in binary aqueous mixtures of THF.