dividing (1) by (2) and rearranging leads to:
(3) yA = aAB xA / [1 + (aAB - 1) xA]
The relative volatility is often a weak function of temperature and therefore can be considered as constant in a reasonable small range of temperature.
Correlation (3) is also the equation of a curve and can be represented in a x-y diagram as shown below:
Constant of relative volatility for multicomponent system
In the most general case the distribution coefficient for component i is:
ki = [gi f Li,pure] / [fi P ]
For multicomponent systems it is useful to define the constant of relative volatility with respect to a reference component r: