Usually, phase equilibrium measurements are performed with pure substances. On the other hand, in technical applications, technical grade substances are used. In this work, the differences in the phase behaviors of these two grades were investigated. The phase behavior of technical grade, nonionic surfactant Genapol X080+technical 1-dodecene+water was studied and compared to the phase behavior of the pure compound. First, binary subsystems (technical 1-dodecene+water; technical surfactant Genapol X080 (R)+water; technical 1-dodecene+technical surfactant Genapol X080 (R)) were studied. The solubility of water in technical 1-dodecene is slightly higher than the solubility of water in pure 1-dodecene. The cloud point curves of technical aqueous surfactant solutions and solutions made from pure surfactant show extreme differences in temperature and shape. The phase behavior of the ternary system was intensively studied visually by measuring Kahlweit's fish at a constant oil/water ratio (alpha=0.5). Tie lines were measured at temperatures between 30 degrees C and 90 degrees C at 10 degrees C intervals. The results were compared to the measured tie lines in a system containing pure substances. The raw material's purity has an enormous influence on phase change temperatures. For the first time, a 4-phase liquid equilibrium was observed in a system containing technical grade substances. Furthermore, the solubility of the surfactant was compared at nearly constant feed concentrations in the aqueous and 1-dodecene-rich phases. (C) 2013 Elsevier Ltd. All rights reserved.