Temperature dependence of thermodynamic properties of leucyl–glycine aqueous solutions from 15 to 45 °C

Abstract

Densities, ultrasonic speeds and refractive index of leucyl–glycine aqueous solutions were determined from 15 to 45 °C, at 5 °C intervals, for the molality range 0–0.3. Apparent molar volumes, V ϕ ,2, and apparent molar isentropic compressions, K S , ϕ,2 , of the solute have been derived from density and ultrasonic speed data. Limiting values of partial molar volumes, V 2 ∞, partial molar isentropic compressions, K S,2 ∞, and partial molar isobaric expansions, E P,2 ∞, have been obtained. Molar refractivities, R m, have been derived from the refractive index using the Lorentz–Lorenz equation. The molar refractivities of the solute, R m,2 ∗ , were calculated by a least squares fitting method. Interesting correlations between the temperature dependence of the different thermodynamic properties studied were found and interpreted in terms of molecular interactions in solution and configurations of the dipeptide skeleton.