Derivation of Konowaloff's Rule from Duhem Margules equation

According to Duhem Margules equation,

If P is the total pressure then-
P = p₁ + p₂
dP = dp₁ + dp₂

This means that the vapour is richer in component 1 (or A) than is the liquid from which is vaporises.

Source: Chemistry for Degree Students By R. L. MADAN