Influence of adsorption on the formation of embryo lunules

Abstract

This paper discusses from a theoretical standpoint the influence of the adsorption of capillarly active substances on the formation of liquid embryo lunules¹ on the surface of imperfectly wetted spheric nuclei. By considering the thermodynamic potential of the system “nucleus-water vapour” before and after the formation of an embryo on the nucleus and, by using the method developed by Kaischew & Mutaftschiew, an expression is derived for the work of formation of an embryo lunule in the presence of adsorption. By taking into account the relation between the contact angle, changed by the decrease in specific surface energy due to adsorption, a general expression is given. This relation is expressed in terms of supersaturation, initial contact angle between the pure nucleus and the liquid, variation in specific surface energy caused by adsorption and between the radius of the nucleus and the radius of the embryo when no adsorption is involved. This formula is most general and under corresponding boundary conditions changes to all known expressions for the work of formation of embryos in homogeneous water vapour on a plane substratum and perfectly and imperfectly wetted condensation nuclei, respectively to those given by Gibbs, Volmer, Krastanov and Fletcher, as well as to the work of formation of embryos in homogeneous water vapour and plane substratum in the presence of adsorption, derived by Kaischew & Mutafschiew. In addition, this formula enables us to discuss embryo formation on condensation nuclei many times larger than the embryo formed at a corresponding supersaturation.

The embryo formed on a portion of the convex surface of the nucleus will be referred to in this paper as lunule.