Abstract: The formation of microemulsion phase for systems containing modified soybean lecithin and the effect of formulationvariables on the physical-chemistry characterization of micioemuision were studied. Soybean lecithin was modified byhydroxychloride in NaClO. Then it was used as surfactant and several short chain alcohols and investigated as cosurfactant.Investigation of the phase and conductance for the microemulsion showed that if C≈3,it could hold the biggest microemulsion.And conductivity would change with water. Modified soybean lecithin was found more effective than lecithin. It was used betterin drug delivery system. And it could be used in reduced amount in cholesterin.

Key words: soybean lecithin, modification, microemulsion, cosurfactant, pseudo-ternary diagrams, conductivity