Molecular interaction studies of l-alanine and l-phenylalanine in water and in aqueous citric acid at different temperatures using volumetric, viscosity and ultrasonic methods

Densities, ultrasonic speeds and viscosities of l-alanine and l-phenylalanine in water and in 0.1 mol·kg− 1 aqueous citric acid solutions were measured over the temperature range (298.15 to 313.15) K with interval of 5 K at atmospheric pressure. From these experimental data apparent molar volume, limiting apparent molar volume and the slope, partial molar expansibilities, adiabatic compressibility, transfer volume, Falkenhagen coefficient, Jone-Dole's coefficient, the temperature derivative of Jone-Dole's coefficient, intermolecular free length, specific acoustic impedance, and molar compressibility were calculated. The results are interpreted in terms of solute - solute and solute-solvent interactions in these systems. It has also been observed that l-alanine acts as a structure breaker whereas l-phenylalanine acts as a structure maker in aqueous citric acid.