Spreading and contraction of a benzene lens on water: A description on the basis of the disjoining pressure

Abstract

In many cases for the droplet of an organic liquid deposited onto the aqueous phase, initial spreading of a droplet is followed by its contraction into a lens. The equilibrium situation will correspond to the coexistence of a liquid lens with a monomolecular or polymolecular film of organic liquid on the surface of the aqueous medium. Benzene on water represents a typical system showing abovementioned behavior. In this paper, we present the equation for the calculation of benzene lens angle based on the disjoining pressure isotherms. We show that the evolution of water content in a benzene lens is responsible for spreading/contraction of the benzene lens on water due to the interplay of different types of surface forces in the benzene film. The influence of water content on the thickness of a benzene film atop of water and on the instant lens angle is considered.