A STABLE TRANSITIONAL FLOW PATTERN IN THE SURFACE-TENSION DRIVEN SPREADING OF ETHANOL WATER SOLUTIONS

When a drop of one ethanol-water solution is placed on the surface of a different ethanol-water solution, the difference in surface tension along the drop boundary causes spreading behavior which depends sensitively on the ethanol concentrations of the two bulk phases. Within a narrow range of concentration combinations, an intricate flow pattern with azimuthal symmetry was observed through the use of schlieren photography. This phenomenon, believed to be a novel Marangoni effect, was characterized in terms of its qualitative features and the region of concentrations for which it occurred. The concentration zone was consistent with a fixed surface tension difference between the two solutions. © 1990, American Chemical Society. All rights reserved.