Partial molar volumes of citric acid and tartaric acid have been determined in water and binary aqueous mixtures of ethanol (5, 10, 15, 20 and 25% by weight of ethanol) at different temperatures and acid concentrations from the solution density measurements. The data have been evaluated by using Masson equation and the obtained parameters have been interpreted in terms of solute-solvent interactions. The partial molar volumes vary with temperature as a power series of temperature. Structure making/breaking capacities of the organic acids have been inferred from the sign of$$[\partial ^2 \phi _V^0 /\partial T^2 ]_{p,} $$ i.e. second derivative of partial molar volume with respect to temperature at constant pressure. Both the organic acids behave as structure breakers in water and water + ethanol.

Relative viscosities for the solutions of oxalic acid and its salts, viz. ammonium oxalate, sodium oxalate and potassium oxalate, at different concentrations have been determined in water and in binary aqueous mixtures of tetrahydrofuran (THF) [5, 10, 15 and 20% by weight of THF] at 298.15 K, and in water and in 5% (w/w) THF + water at five different temperatures. The data have been evaluated using the Jones-Dole equation and the obtained parameters have been interpreted in terms of solute-solute and solute-solvent interactions. The activation parameters of viscous flow have been obtained which depicts the mechanism of viscous flow. The oxalic acid and its salts behave as structure breakers in water and in binary aqueous mixtures of THF.