Study of thermodynamic properties of aqueous binary mixtures of l-threonine, l-valine and l-arginine at low temperatures (T/K = 275.15, 279.15 and 283.15)

Abstract

The experimental values of density (ρ) and speed of sound (u) in aqueous solutions of l-threonine, l-valine and l-arginine are reported at T=(275.15, 279.15 and 283.15)K. The derived parameters, apparent molar volume of solute (Vϕ), isentropic compressibility (kS) of solution, apparent molar compressibility of solute (kϕ) in dilute aqueous solutions of l-threonine, l-valine and l-arginine have been computed using values of density (ρ) and speed of sound (u). The limiting values of apparent molar volume of solute (Vϕ0), apparent molar isentropic compressibility of solute (kϕ0) and apparent molar expansivity (ϕE0) are also obtained. The results are discussed in the light of solute-solvent interactions, and structure making and structure breaking abilities of the solute in aqueous medium. From the results obtained for dϕE0/dT, it has been observed that l-threonine behaves as a structure maker, whereas l-valine and l-arginine act as structure breakers when dissolved in water at temperatures studied in present work.