CHAP. 7: PHASE EQUILIBRIA [CONTENTS] 201
0 x^11
0
1
y 1
6
x 1 =y 1
Obr.7.8:y−xdiagrams of two two-component systems. The bold line shows the dependence of the
vapour phase composition on the liquid phase composition for a system with a positive azeotrope; the
azeotropic point is indicated by the arrow. The thinner line shows the same dependence for a system
without an azeotropic point.
Solution
From relations (7.24) and (7.26) it follows that at the azeotropic point
γi=p/psi
and thusγ 1 = 1. 43 andγ 2 = 1. 69.
Note: In order to compare mutual volatility of two components in a mixture,relative
volatilityis defined as
αij=
yixj
xiyj
. (7.30)
From (7.26) we can see that at the azeotropic point, relative volatilities equal 1.
Azeotropic point in a two-component system