Partial Pressures in Liquid Mixtures and Osmotic Pressures
  We have shown in this investigation that the partial pressure can be defined uniquely as each wall pressure exerted by a component in liquid mixtures, and is an important observable physical quantity. As a consequence of this definition, the law of partial pressures is applicable to liquid mixtures with strong interactions. Furthermore, it has been shown here that the gas-liquid phase equilibrium in mixtures is established by the balance of each partial-pressure for every component between the two phases. Hence, for a dilute solution Henry's law, Raoult's law and van't Hoff's law can be derived on the basis of the concept of partial pressure. 
Junzo Chihara and Mitsuru Yamagiwa
cond-mat.stat-mech