Partial molar volumes of organic solutes in water. XX. Glycine(aq) and L-alanine(aq) at temperatures (298 to 443) K and at pressures up to 30 MPa

Density data for dilute aqueous solutions of two amino acids (glycine, L-alanine) obtained using a flow vibrating-tube densimeter are presented together with partial molar volumes at infinite dilution (standard molar volumes, V-m,V-2 degrees) calculated from the measured data. The experiments were performed at temperatures from (298 up to 443) K at pressures close to the saturation line of water, at pressures in the range from (15 to 17) MPa, and at 30 MPa. Values of an analogue of isothermal compressibility, kappa(T,2)degrees = -(1/V-m,V-2 degrees)(partial derivative V-m,V-2 degrees/partial derivative p)(T), are also evaluated. Maxima on the curves V-m,V-2 degrees(T) and kappa(T,2)degrees T) are observed and discussed. The new data along with literature values of standard molar volumes and heat capacities are used for generating the recommended parameterization of an equation of state for standard molar thermodynamic properties of the aqueous amino acids. (C) 2009 Elsevier Ltd. All rights reserved.