Phase equilibrium of a liquid droplet formed on a solid particle

An equation of state of a two-phase system, deduced from the principles of classical thermodynamics, is used to illustrate the effects of interface curvature, electric charge, a soluble substance, and of disjoining film pressure on the equilibrium of a liquid droplet formed on a solid particle. The former three effects have been widely discussed in the past, whereas the effect of the disjoining film pressure has not been explored. The focus of the paper is, therefore, placed on the effect of the disjoining film pressure on the droplet equilibrium. Opposing the action of surface tension, the disjoining pressure is shown to lower the equilibrium vapour pressure at constant temperature and to increase the equilibrium temperature at constant pressure in comparison to the equilibrium in the reference state. This interplay provides a way bringing experimental findings in a better agreement with theoretical models.