called critical micelle concentration (CMC). However, stud-Surface tension of aqueous solutions was measured for sodium ies of the thermodynamic quantities of the adsorbed film taurodeoxycholate, as a typical example of the bile salt comderived from surface tension measurements have been made pounds, in the temperature range 20 to 35ΠC at 2.5ΠC intervals to only a very limited extent; the measurements provide an and concentration range 0 to 7 mmol kg 01 . We examined thermoexperimental approach to the study not only for the solution dynamic quantities obtainable from the surface tension measureproperties in an aqueous phase but also for the lateral interacments according to the thermodynamic relations given by K. Mototion in the surface film. The peculiar property that the aggremura [J. Colloid Interface Sci. 64, 348 (1978)]. Sodium taurodegation occurs gradually, in contrast to common surfactants, oxycholate was strongly adsorbed and formed the saturated makes thermodynamic studies of the structure and properties adsorbed film at low concentrations. However, the gaseous/expanded phase transition does not take place in the film. The ther-of the surface films interesting, as they could provide further modynamic quantities associated with adsorption did not change insight not only into the aggregation process but also into as markedly at the critical micelle concentration as those observed the molecular interactions in the surface films.
for typical surfactants. It was suggested that molecular interac-This study is intended to evaluate thermodynamic quantitions between sodium taurodeoxycholate molecules in aqueous soties accompanying the adsorption of NaTDC up to the conlutions and adsorbed films are too weak to induce critical changes centration range where aggregation occurs and to examine in the thermodynamic quantities.