Sodium perfluorooctanoate/cetyltrimethylammonium bromide, n-propyl alcohol/butyl alcohol, octane and brine can form middle phase microemulsion. Its optimum components were found by using perpendicular experiment. The effect of salinity, concentration of surfactants and alcohol, kinds of hydrocarbon to the formation and characteristics of the middle phase microemulsion have also been investigated. Microstructure of the microemulsion was determined by infrared spectrum. The OBS/CTAB system was compared with CTAB and AOT/CTAB systems. The results are of importance to practical and theoretical research.

Key words: SURFACTANTS, INFRARED SPECTROPHOTOMETRY, ORTHOGONAL TEST, MICRO-STRUCTURE, N-BUTANOL, MICROEMUSION, N-PROPYL ALCOHOL (=1-PROPANOL)