Some books received

Abstract

The solubilization of p-xylene by “normal” micelles has been measured at 20°C for the system sodium octanoate/decano/water/xylene. It was found, empirically, that the xylene solubilization limit was a linear function of the concentration of decanol at every surfactant concentration studied between the critical micelle concentration and the phase boundary. The slopes and intercepts of least-squares fits to the data were not constant, however, but depended on the surfactant concentration. From an analysis of the behavior of the slopes and intercepts we reach the following conclusions: (i) The second and third critical concentrations previously reported for solutions without decanol also occur in solutions which contain decanol. (ii) In the phase diagram of the sodium octanoate/decanol/water system, the second critical concentration is a line which extends from the second critical concentration point on the sodium octanoate/water line to the apex of the three-phase triangle of solution/mesomorphic phase C/mesomorphic phase D. (iii) A similar “line” connects the third critical concentration “point” of the binary system with the three-phase triangle of solution/phase D/phase E. (iv) From the formal analogy between the roles of these two critical concentration lines in the phase diagram, it can be inferred that C must be a true mesomorphic phase, and not an emulsion of D as has been suggested in the literature. Finally, the solubilization data are discussed with regards to the X-ray scattering study of Svens and Rosenholm [J. Colloid Interface Sci., 44, 495 (1973)] and some tentative descriptions of solubilization mechanisms are inferred.