The physicochemical properties of mixed polymeric surfactant systems were studied with different techniques. A binary system consisting of lignosulfonate and petroleum sulfonate and a ternary system consisting of two different lignosulfonates and petroleum sulfonate were studied with respect to phase behavior, interfacial tension, specific conductivity, and pH measurements. In addition, the original lignosulfonates were subjected to ion exchange from sodium to calcium or vice versa, and the effects were investigated. (C) 2003 Wiley Periodicals, Inc.