It has been generally recognized that studies of thermodynamic and transport properties of surfactants are important to understand their behavior in solutions. One of the important properties of surfactants 1s the association of their amphiphilic molecules into micellar aggregates in aqueous solutions [1] . The micellization study of surfactants in solution is important because the performance of the surfactant in many interfacial processes depends on its concentration and orientation at the interface [2]. The surfactant concentration where the micelles start to form is known as the critical micelle concentration, abbreviated to CMC[1].The critical micelle concentration (CMC) is a key thermodynamic quantity of surfactant- water mixture.A great deal of research has been devoted to determining the CMC experimentally and through predictive techniques [3]. The CMC can be influenced by different factors such as chemical structure of surfactant (type of surfactant (ionic or non-ionic), alkyl chain length, head groups, valency of the counterion and different groups on alkyl chain), temperature, pressure and cosoiute[l]. Polymer/surfactant mixtures are common in bioiogicai systems. Interaction of surfactants with water-soluble polymers has been extensively studied for their widespread applications in industry.Because of their characteristic physicochemical properties at different possible combinations the polymer and ionic surfactant mixed systems are interesting[ 4] . .In this study The vapor-liquid equilibria properties of Sodium 1-hexanesulfonate (C5S03Na) in pure water and in aqueous poly( ethylene glycol) (PEG) solutions were determined at 298.15k below and above the critical micelle concentration(CMC).
