ABSTRACT
This chapter presents the phase diagram of a quaternary mixture and investigates "The phase diagrams of several water-surfactant-alcohol (W, S, A) and water-surfactant-oil (W, S, O) mixtures. They display a rich variety of phases and also complex multiphase regions where two or three liquid isotropic and mesomorphic phases are in equilibrium. Quaternary mixtures of water-oil-surfactant-alcohol (W, 0, S, A) are also expected to exhibit a complex range of phase behavior and to offer an interesting area for observing a large variety of phase transitions including critical phenomena. The study of the phase diagram of the water-dodecane-pentanol-sodium dodecyl sulfate system has permitted us to locate a line of critical points and two critical end points. Phase diagrams analysis has shown the existence of a critical line on the boundary of the microemulsion region. The diagram obtained shows many common features with those of simpler surfactant systems containing only two or three components.
