Conductance of foam films

Abstract

Simultaneous measurements of thickness and conductivity have been made on foam films drawn from aqueous solutions of a neutral surface-active agent, [graphic omitted], containing added electrolyte (NaBr). This compound gives formally uncharged surface monolayers which adsorb inorganic ions to produce an electrolyte excess in the film core. The films rupture at a critical thickness and are unstable when their thickness falls below that corresponding to the secondary minimum in the Derjaguin-Landau Verwey-Overbeek theory of colloid stability. Bikerman's theory of surface conductivity has been used to calculate the zeta potential at the film core interface; this decreases with increasing electrolyte concentration.