Hydrodynamics of thin liquid films. Experimental investigation of the effect of surfactants on the drainage of emulsion films

In our previous theoretical work on the velocity of thinning of emulsion films we reached the conclusion that this velocity differs only slightly from that for foam films when the surfactant is soluble in the dispersion medium and is equal to that for a system without any surfactant when the surfactant is soluble in the dispersion phase. In the present work these results are checked experimentally by investigating the effect of different concentrations of surfactant in the dispersed phase (a) on the velocity of thinning of films, containing very low concentrations of surfactant soluble in the dispersion medium and (b) on the life time of films from pure liquids. The experiments show that within the precision limits of the experimental methods used, the presence of surfactant in the dispersed phase has no effect on the velocity of thinning and life time of emulsion films in accord with the theoretical conclusions.