Reverse Flow of Mixed Surfactant Solutions after Their Capillary Rise

The reverse flow (i.e., the efflux from glass capillaries occurring after the stop of capillary rise) of mixed aqueous solutions of nonionic (Triton X-100) and cationic (cetyl- and dodecyltrimethylammonium bromides) surfactants is studied. The effect of electrolytes (salts and acids) on the process kinetics and the wetting in these systems is investigated. Possible causes of the reverse flow are discussed. They are related to the peculiar features of the interaction of nonionic and cationic surfactants with glass and to the differences in the surfactant adsorption from quiescent and moving solutions. It is shown that the wetting by the mixed surfactant solutions, including its kinetics, can be controlled by the addition of electrolytes.