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

1589-1593Densities (ρ) 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 (Vϕ) and partial molar volumes of the amino acids (Vϕ0) at infinite dilution have been evaluated. The data have been combined with the known values of Vϕ0 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 (ΔVϕ0) 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