The hydrotrope action of sodium xylenesulfonate on the solubility of lecithin

The activity of sodium xylenesulfonate in aqueous solution was determined b y vapor pressure measurements, the results of which were transformed to mea n activities. In addition, surface tension, conductivity, and partial molar volume were determined to obtain complementary information about potential association structures. No sudden change was observed, indicating the asso ciation to take place in the concentration range where the increased solubi lity of lecithin was observed, contrary to the case of surfactant micelliza tion. The solubilization of lecithin in the aqueous solutions of sodium xyl enesulfonate showed the association to be cooperative between the two amphi philes. A model is proposed for the interpretation of the catastrophic inco rporation threshold concentration observed in the solubility curve of lecit hin. (C) zool Academic Press.