Volumetric studies of L-valine and L-leucine in aqueous solutions of NaBr at 298.15 K

Densities (P) of the amino acids, L-valine and L-leucine, in aqueous solutions of sodium bromide (0.05-1.0 mol kg(-1)) have been measured at 298.15 K. From these densities, apparent molar volumes (V-phi) and partial molar volumes of the amino acids (V-phi(0)) at infinite dilution have been evaluated. The data have been combined with the known values of V-phi(0) of glycine, and L-alanine in aqueous NaBr solutions at 298.15 K in order to determine the group contributions. The trends of transfer volumes (Delta V-O phi(0)) have been interpreted in terms of solute-cosolute interactions on the basis of a cosphere overlap model. Pair and triplet interaction coefficients have also been calculated from transfer parameters.