Abstract: The stability of foams has been studied in aqueous and nonaqueous solutions of various surfactants. In aqueous and ethylene glycol solution of surfactants, surface viscosity played an important role in stabilizing foams.Presence of liquid crystal increased the surface viscosity as well as the viscosity of bulk solution and as a consequence increased thestability of the foam. In xylene and n-hexane solutios of surfactants the stability of the foam was very poor,for the molecules of the surfactant were incapable of forming adsorption film in the air-solution interface. In case the concentration of the surfactants was much higher than that of the non-polar solvent in foaming system,the foam stability could be enhanced by liquid crystal. Silicone oil appeared a good defoaming agent in aqueous system, but it became badwhen the amount of the liquid crystal increased.

Key words: Foam, Lyotropic liquid crystal, Surface viscosity