Phase transition processes in surfactant adsorption layers

Adsorption data in the form of surface tension vs hulk concentration isothe rms having strong changes in the: slope have often been discussed in the li terature in terms of phase transitions in the adsorption layer. It will be shown thermodynamically that these apparent kink points in the isotherms ar e unreal. A phase transition would cause a completely opposite change in th e isotherm. Experimental surface tension data for sodium octanoate and dode cyl ammonium chloride obtained from the literature are reinterpreted on the basis of the Frumkin and reorientation isotherms. (C) 2000 Academic Press.