There exist many methods for the determination of liquid-vapour equilibria, some of them being of a dynamic, while others of a static character^[1].Recent criticisms^[2] point out that the latter may be regarded upon as being more reliable, since it seems doubtful whether true equilibria may be reached by the use of dynamic methods. Fulfillement of the wellknown Gibbs-Duhem relations is an unambiguous criterion by which to decide whether experimental points of an isothermal phase diagram correspond to true thermo-dynamic equilibrium.