Volumetric Properties of Potassium Dihydrogen Citrate and Tripotassium Citrate in Water and in Aqueous Solutions of Alanine at T = (283.15 to 308.15) K

Abstract

Densities and sound velocities for solutions of potassium dihydrogen citrate (KH2Cit) and tripotassium citrate (K3Cit) in aqueous solutions of (0.00, 0.23, 0.47, and 0.72) mol·kg−1 of alanine have been determined experimentally at T = (283.15, 288.15, 293.15, 298.15, 303.15, and 308.15) K at atmospheric pressure. From these experimental data, the apparent molar volume and isentropic compressibility values have been evaluated and fitted to a Redlich−Mayer-type equation. The results show positive transfer volumes at infinite dilution for electrolytes from water to aqueous alanine solutions, and these values increase with the concentration of alanine. The apparent molar isentropic compressibility of both KH2Cit and K3Cit in aqueous alanine solutions is negative, which implies that the water molecules around these salts are less compressible than the water molecules in the bulk solutions. It was found that the effect of alanine concentration on the apparent molar volume and isentropic compressibility of K3Cit...