# About Azeotrope.info

This application brings for you azeotropic data (azeotrope boiling point/temperature and composition), based on vapor-liquid equilibrium calculations. So the program does not provide stored experimental data, but predicts them theoretically.

## Method of calculation

At an azeotropic point the composition of vapor- and liquid phases are identical (*x*), and the bubble- and dew point curves have a local extrema.

_{i}= y_{i}Take an objective function that measures the relative deviation of the compositions between the vapor- and liquid phases:

*f*

_{i}= (x_{i}- y_{i}) / x_{i}At every

*x*points in the composition space, where

*f*must be an azeotropic point. (Except the corner points representing the pure components (

_{i}= 0*i*), where

*x*and

_{i}= 1*x*.) The program uses multi-variate Newton-Raphson search to locate these points.

_{j≠i}= 0The composition of the vapor phase is calculated according to the modified Raoult's law:

*p*

_{i}= γ_{i}• p_{sat.,i}• x_{i}*y*

_{i}= p_{i}/ Σ_{j=1→N}p_{j}where:

*p*is the partial pressure of component_{i}*i*in the vapor phase of the mixture*γ*(gamma) is the activity coefficient of component_{i}*i*in the liquid mixture*p*is the vapor pressure of saturated pure component_{sat.,i}*i**x*is the liquid phase mole fraction of component*i**y*is the vapor phase mole fraction of component*i*

*Find more information about azeotropes at Wikipedia*