The highest temperature is related to water and the lowest temperature is attributed to diethyl ether (ether)/water system. The ternary diagram and residue curve mapare shown in Figure 2b. These charts are extracted using the UNIQUAC thermodynamic model in Aspen plus simulation software for the pressure of 1 atm. The ternary diagram shows location of azeotropes and a liquid-liquid envelope in the system in which the ether/water azeotrope lies closely to the boundaries of this envelope. The azeotropes limit separation of component in single distillation column and more complicated process is needed to separate components. Hence, selection of suitable thermodynamic model is important when accurate vapor/liquid/liquid separation is desired. The tie-lines in the residue curve map are initiated from the lowest temperature and sloped toward the highest temperature (water), in which a stream containing water with small content of ethanol is recovered in the process.