PHASE-EQUILIBRIA AND PHASE-STRUCTURE IN THE TERNARY-SYSTEMS SODIUM ORPOTASSIUM OCTANOATE OCTANOIC-ACID WATER

Two isotropic solution regions and several liquid crystalline regions occur in the ternary system sodium octanoate-octanoic acid-water at 20 -degrees-C. The solution regions are an aqueous solution and a solutio n of sodium octanoate and water in liquid octanoic acid. A region disp laying one-dimensional lamellar structure is located in the center of the phase diagram. A region along the soap-water axis has a two-dimens ional normal hexagonal structure. Another region at high octanoic acid content has a reversed hexagonal structure. Along the soap-fatty acid axis the acid-soap 2NaC8:1HC8 in crystalline state is found. X-ray an d density findings for the various phases are presented, and structura l parameters for the different liquid crystalline phases are estimated . The phase behavior of the potassium soap system is similar to that o f the sodium system. The isothermal ternary phase diagram of a soap, t he corresponding fatty acid and water provides information about the i onization state of the system, from the unionized fatty acid to the fu lly ionized soap.