Vapor pressure and surface tension of the aqueous solution of sodium dodecyl sill-fate(SDS)/polyethylene oxide(PEO) were measured at 298.15, 308.15 and 318.15K respectively, the coucentration of PEO was 0.5%, and the concentration of SDS (mnsds ) was up to 80 mmol.kg-1 The activity coefficient of water at different temperatures was calculated. The effcct of intermolecular interactions on the vapour pressure was discussed. From vapo pressure and surface tension data, the critical aggregate concentration (CAC) and polymer saturation point (PSP) were ob-tained.
