The isobaric vapor-liquid equilibrium (VLE) diagram of the immiscible binary mixture composed of benzene and water presents a heteroazeotrope. This Demonstration computes VLE data and displays the isobaric VLE diagram as well as the boiling temperature and composition of the heteroazeotrope for values of the total pressure to be set by the user. The NRTL (Non-Random Two Liquid) model, derived by Renon and Prausnitz, is used to compute the activity coefficients in the liquid phase, which are used in the modified Raoult's law: where or 2, is the saturated vapor pressure of component , is the activity coefficient, and are the liquid and vapor mole fractions of component and is the total pressure.