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

Abstract

Densities (<i>ρ</i>)<i> </i>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 (<i>V</i>_ϕ) and partial molar volumes of the amino acids (<i>V</i>_ϕ⁰) at infinite dilution have been evaluated. The data have been combined with the known values of <i>V</i>_ϕ⁰ 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 (Δ<i>V</i>_ϕ⁰) 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.