Partial molal volumes and adiabatic compressibilities of transfer of glycine and DL-alanine from water to aqueous sodium sulfate at 288.15, 298.15 and 308.15 K

Abstract

The partial molal volumes (φ_v^°) and partial molal adiabatic compressibilities (φ_ks^°) of glycine and DL-alanine have been obtained in water and aqueous solutions of 0.5, 1.0 and 1.5 mol kg^-1 sodium sulfate at 288.15, 298.15 and 308.15 K from measurements of density and ultrasonic velocity. Their variations with temperature and their transfer properties from water to aqueous solutions of sodium sulfate have also been obtained. The results have been interpreted in terms of the hydration of the hydrophobic and hydrophilic parts of the amino acids. The φ_v^° or φ_ks^° values of the amino acids were regressed to a general equation φ_v^° or φ_ks^°=a+bm+cm²+(T-298.15)(d+em+fm²), where m is the concentration of sodium sulfate (01.5 mol kg^-1) and T is the temperature (288.15–308.15 K). The calculated values from the regressed equations are in good agreement with those obtained experimentally with a maximum standard deviation 0.18 cm³ mol^-1 for φ_v^° and 10^-4 cm³ mol^-1 bar^-1 for φ_ks^°.