Lyotropic liquid crystal from nonionic surfactant (AEO-9)/n-octane/n- butanol/water were studied at 20℃ to determine the phase regions and obtain some typical photographs by using microscope with polarized- light. The ^2H NMR methods were used to determine the exact liquid crystals' structure. It was found that the structure varied from mixed W/O type microemulsions and lamella liquid crystals through single lamella liquid crystals, mixed lamella and hexagonal liquid crystals, to O/W type microemulsion in the liquid crystal region with the addition of water. The geometrical dimensions were determined by small angle X-ray diffraction. For this lamella liquid crystal the results indicated a linear increase in interlayer spacing with addition of water and a pronounced decrease with addition of AEO-9 in the system. The data of interlayer spacing were obtained and then calculated the ratio of oil layer and water, which ranged from 0.1 to 0.6. On the basses of characteristic and composition of lamella liquid crystal, the liquid crystal forming equation is introduced for the first time, and its position and region shape could also be determined in the pseudo-ternary phase diagrams. The result could proven by experiment.

Key words: LYTROPIC LIQUID CRYSTAL, SURFACTANTS, POLYETHYLENE OXIDE, BUTANOL, OCTANE, MULTICOMPONENT SYSTEM, PHASE DIAGRAM