The interfacial tensions between ethylene and an aqueous solution of SDS were measured using the pendant-drop method at 274.2 and 278.2 K and in the pressure range from 0.1 to 3.1 MPa, including hydrate formation points. The concentrations of sodium dodecyl sulfate (SIDS) aqueous solution were 0, 1 00 300, 500 600, 700, 800, 900, and 1000 ppm. The effects of pressure on the critical micelle concentration (CMC) and the surface excess concentration were Studied. It was demonstrated that both the CMC and the saturated surface excess concentration decreased with the increase of pressure. (c) 2005 Elsevier Inc. All rights reserved.