A study of partial molar volumes of citric acid and tartaric acid in water and binary aqueous mixtures of ethanol at various temperatures

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 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.