Densities and excess molar volumes of formic acid, acetic acid and propionic acid in pure water and in water plus Surf Excel solutions at different temperatures

Densities, rho of the systems formic acid, acetic acid and propionic acid in water and in 0.05% and 0.1% Surf Excel (SE) solutions in water were measured at temperatures 303.15, 308.15, 313.15, 318.15 and 323.15 K respectively covering the whole composition range. Excess molar Volumes, V(m)(E) for the systems were found to be negative and their values were found, to increase with chain length of carboxylic acid. Densities and excess molar volumes have been plotted against mole fraction of the solutes (X(2)). All these properties have been expressed satisfactorily by appropriate polynomials. No appreciable change of the densities and excess molar Volumes were observed by the addition of surfactant (0.05% and 0.1%) to the studied systems. All attempt has been made to explain V(m)(E) in terms of hydrophobic hydration and hydrophilic effect of the solutes. An explanation of V(m)(E) in terms of hydrophobic hydration and hydrophilic effect of the solutes is offered.