Details

Immiscible components do not mix in the liquid phase, and each independently exerts its saturation pressure and ; the subscripts and refer to benzene and water. The equations are the same for the other organics (toluene, -hexane). The total pressure above the two immiscible liquids is equal to the sum of their saturation pressures:

.

The saturation pressures are calculated using the Antoine equation:

,

where is the saturation pressure of (bar); , and are Antoine constants; and is temperature (°C).

For the benzene-water system, for conditions where benzene condenses, the dew point curve is:

,

where is the mole fraction of benzene in the vapor phase.

For conditions where water condenses, the dew point curve is:

,

where is the mole fraction of water in the vapor phase and .

The screencast video at [1] explains how to use a similar Demonstration.

Reference

[1] Immiscible Liquids on Pressure-Composition Diagram [Video]. (Feb 1, 2018) www.colorado.edu/learncheme/thermodynamics/ImmiscibleLiquidsPxy.html.