Abstract: The methods of gas-liquid chromatography and volume change on mixing have been applied to study molecular complexation between some C₈ aromatics and sulfolane. The equilibrium constants of complexes of the aromatic with sulfolane have been measured by both reference stationary phase method and mixed stationary phase method. The volume change on mixing for binary systems of sulfolane with five C₈ aromatics especially for the system of sulfolane with styrene, are all negative. The volume effect of binary systems of propylene carbonate with C₈ aromatics are also contracted but the extent of contraction are far lower than the former.