Partial molar volumes and adiabatic compressibilities at infinite dilution of aminocarboxylic acids and glycylglycine in water and aqueous solutions of sodium sulphate at (288.15, 298.15 and 308.15) K

Abstract

The partial molar volume and partial molar adiabatic compressibilities at infinite dilution of dl-aminobutanoic acid, dl-norvaline, β-alanine, 4-aminobutanoic acid, 5-aminopentanoic acid, 6-aminohexanoic acid and glycylglycine have been obtained in water and aqueous solutions of (0.5, 1.0 and 1.5) mol · kg −1 sodium sulphate at (288.15, 298.15 and 308.15) K from measurements of density and ultrasonic velocity. A qualitative interpretation of the results has been given using the Kirkwood model and nature of the interactions in solutions. A model, derived from Scaled Particle Theory, has been used for quantitative explanation of partial molar volumes and for the understanding the volumes of interaction. The results distinguish the behaviour of α-amino acids from that of α,ω-amino acids, and of the “less polar” 5-aminopentanoic acid from that of the analogous, but “more polar”, glycylglycine in solution. These findings are in agreement with previous studies in aqueous solutions and they support the water-structure making ability of sodium sulphate.