This Demonstration shows the residue curve of a non-ideal ternary mixture composed of chloroform, acetone, and methanol at a total pressure of 10 atm. Deviation from ideal gas phase behavior must be considered. Indeed, the vapor-phase fugacity coefficient is computed using the Soave–Redlich–Kwong equation of state. This mixture presents three binary azeotropes and a ternary azeotrope, marked in the ternary diagram by for . Azeotropes appear as extrema of the residue curves. You can drag the locator and the program will plot the residue curve passing through the locator position. The location of the ternary azeotrope has been determined separately since it is neither a stable nor an unstable node. Compositions of all binary azeotropes are obtained from the residue curve calculations, as follows:

Binary azeotropes:

Methanol-Chloroform: 45.54% Chloroform

Methanol-Acetone: 42.75% Acetone

Chloroform-Acetone: 70.90% Chloroform

Ternary azeotrope:

Methanol-Chloroform-Acetone: 6.66% Chloroform and 29.17% Acetone

VLE data is computed using the following formula (the gamma-phi equation): where and are the vapor and liquid mole fractions of component , is the total pressure, is the saturation vapor pressure of component , and and are the vapor-phase fugacity coefficient and the liquid-phase activity coefficient determined using the Soave-Redlich-Kwong equation of state and the Wilson model, respectively.

For more information, see

M. F. Doherty and M. F. Malone, Conceptual Design of Distillation Systems, New York: McGraw-Hill, 2001.

H. Binous, A. Wakad, and S. Ben Achour, "Residue Curve Map Calculation of a Ternary Mixture," Computer in Education Journal, 16(4), 2006 pp. 32-35.