Permeability of common black foam films to gas. Part 2

Abstract

The film permeability coefficients K for permeation of air through common black films (CBF) have been experimentally measured using the stationary bubble method described earlier (R. Krustev, D. Platikanov and M. Nedyalkov, Colloids Surfaces A: Physicochem. Eng. Aspects, 79 (1992), 129.) The dependence of K on LiCl concentration and temperature T have been studied for CBF from sodium dodecyl sulfate (SDS) + LiCl aqueous solutions. The K(T) dependence for the system SDS + NaCl has also been studied. The results prove our hypothesis that the film permeability is determined mainly by the monolayer permeability K ml of the adsorption layers. The K ml values increase with increasing distance between the monolayers (i.e. the film thickness) and tend to a constant value. K ml and K depend on the specific adsorption of the counterions in the dodecyl sulfate monolayer. The CBF with Li + ions are essentially more permeable than those with Na + ions, which are more strongly adsorbed.