Studies on the Phase Behavior of the SDBS/ Alcohol/n-Heptane/Brine System

Based on the orthogonal design, the optimal formation conditions of the middle phase microemulsions in the sodium dodecyl benzene sulfonate （SDBS）/n--butanol/n-heptane/brine system were obtained as follows’ C_sDBS（%）= 1.0-2.0, C_n-butanol （%）=2.5-4.0, and C_NaCl（%）= 1 .8 2.2. The effect of the concentrations of NaCl, n--butanol, SDBS, and the kind of alcohols （n-propanol, n-butanol, and n-pentanol）on the phase behavior of microemulsions, the optimal salinity （S^*）, and the length of salinity （△S）were investigated.Some rules and data were obtained about the formation and characterities of the middle--phase microemulsions.