Activity of Water, Osmotic and Activity Coefficients of Sodium Glutamate and Sodium Aspartate in Aqueous Solutions at 310.15 K

The vapour pressures of aqueous solutions of sodium L-glutamate (mi = 0.05–0.57 mol kg–1) and sodium L-aspartate (mi = 0.005–0.48 mol kg–1) were precisely measured at T = 310.15 K and the activity of water and the osmotic and activity coefficients of the solutes were calculated from these data. The concentration dependence of the osmotic coefficients is described with the help of the Pitzer equation and the mean spherical approximation (MSA). It is shown that it is possible to describe thermodynamic properties of sodium aspartate and sodium glutamate solutions up to 0.5 molkg–1 with distance parameter R as the single fit parameter.