Phase diagrams were constructed for the NaCl/H2O/SDS/BuOH/n-C8H18 system at BuOH:SDS wt. ratio 4 at various salinities. The diagrams indicate that an increase in salinity leads to expansion of the phase-sepn. region and the formation of a 3-phase area including a middle microemulsion phase. The d., viscosity, elec. conductivity, and n of the middle microemulsion phase have a close relation to the optimal salinity and the transition of microemulsion microstructure. The IR measurements indicate that the H bond strength in the oil phase is notably stronger than that in the middle microemulsion phase.

Key words: INFRARED SPECTROPHOTOMETRY, WATER, SODIUM CHLORIDE, ASSOCIATION, HYDROGEN BONDS, SODIUM SULFATE, C12 COMPOUNDS, PHASE STRUCTURE, PHASE DIAGRAM, MICRO-STRUCTURE