Tension of liquid films and contact angles between film and bulk liquid

Abstract

The relationships between the tension Δ of a thin liquid film, the disjoining pressure Π in it, and the contact angle θ between the thin film and bulk liquid with which the film is in equilibrium, are considered. The possibility of measuring θ is discussed and two methods are suggested : (a) a “topographic method” suitable for the measurement of small θ, and (b) an “extension method” for larger θ. Both methods refer to microscopic films in hanging biconcave drops.