Thermodynamic transfer functions at infinite dilution and clathrate formation of ethanolamines in water

The ultrasonic velocities and densities of solutions of water in various bi nary aqueous solutions of ethanolamines were measured over the full range o f compositions at 298, 308 and 318 K. The experimental data in the dilute r egion with mole fraction of water <0.1 was analyzed to determine the partia l molar volume and adiabatic compressibilities at infinite dilution. Compre ssibility isotherms intersect approximately at a common point for triethano lamine (TEA), methyldiethanolamine (MDEA), dimethylethanolamine (DMEA) and diethylethanolamine (DEEA) and this is attributed to the formation of quasi -clathrate-like structures in the liquid solutions. The standard thermodyna mic transfer functions were calculated to evaluate the environment of water at infinite dilution in these systems. The transfer functions of water bet ween the various ethanolamines are considerably larger for ethanolamines th at differ in their degree of hydrophobicity. (C) 2000 Elsevier Science B.V. All rights reserved.