Effect of temperature on the partial molar volumes, partial molar compressibility and viscosity B-coefficients of DL-4-aminobutyric acid in water and in aqueous sodium chloride solutions

Abstract

Density, sound velocity and viscosity of DL-4-aminobutyric acid (GABA) in water and in aqueous sodium chloride solutions have been measured at (293.15, 298.15, 303.15, 308.15 and 313.15)K. The apparent molar volumes and the apparent molar compressibilities were calculated at each temperature from the experimental density and sound velocity data. Limiting values at infinite dilution of the partial molar volumes and the partial molar compressibilities of GABA in water and in aqueous sodium chloride solutions were determined through extrapolation at each temperature. The relative viscosity data were adjusted by a least-squares method to a second order equation as proposed by Tsangaris-Martin to obtain the viscosity B coefficients. The influence of temperature on the behaviour of viscosity and the volumetric properties is discussed in terms of molecular interactions.The results confirm that hydrophilic hydration is predominant for GABA in aqueous solution. The addition of NaCl leads to an increase of the partial molar properties at infinite dilution and the viscosity B-coefficients, suggesting that the sodium and the chloride ions interact directly with the zwitterion, reducing the electrostriction of water molecules.