The pressure-composition phase diagram for two immiscible liquids, benzene and water, is at constant temperature. Set the temperature with a slider to change the saturation pressures. Set the overall benzene mole fraction with a slider. The bar graph shows the moles of liquid water (blue), liquid benzene (orange) and vapor (green), which contains both components. The system contains one mole total. You can change the piston height to change the pressure and the amounts of each phase. At a given temperature, all three phases co-exist at only one pressure. When the piston height increases at this pressure, one of the liquid phases completely evaporates before the pressure decreases. Select "piston-cylinder" instead of "amounts of each phase" to view a representation of a piston-cylinder with the volume of each phase on a log scale.