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An experimental study of the spreading and dissolving of thin liquid films under the action of surface forces is presented. The method consists of the continuous feeding of a liquid over the surface of another liquid into which it dissolves; the steady film thus obtained covers only a part of the supporting liquid surface, dependent on the flow rate of the liquid fed. The dependence of the radius of the film contour on flow rate and concentration driving force is obtained for various film forming liquids dissolving into water. By using a Schlieren technique the film contour and the flow pattern outside the film contour are studied, several structures being evidenced.Experiment and theory (3 to 7, 10, 12 to 14, 16 to 18) show that when the Marangoni effect controls the hydrodynamics of the fluid-fluid interfaces the mass transfer is particularly enhanced. The hydrodynamic phenomena which are triggered by the Marangoni effect are complex (3, 5, 6, 11, 1 4 ) owing to the interfacial turbulence it may produce, and their detailed examination is difficult. We have examined a less involved manifestation of the Marangoni effect related to dissolving of thin liquid films, and the aim of this paper is to present our observations.The starting point was our observation that during the reciprocal dissolving of two pure partially miscible liquids (for example, isobutanol and water), conditions for the occurrence of the Marangoni effect may appear. In an open dish a layer of i-butanol was placed above a layer of water. If the lighter i-butanol is present only in amounts sufficient to form a thin continuous film over the water surface, its thickness decreases continuously as a result of the combined effects of evaporation and dissolving. At a certain moment, the continuous film breaks down and regions of the supporting liquid surface become free of i-butanol; thus zones, across which surface tension gradients are present, appear. The rapid movements due to the Marangoni effect now taking place in the plane of the free surface of the supporting liquid lead to an intense agitation, similar to that of a boiling liquid. The agitation ceases suddenly when all the i-butanol film has dissolved. Somewhat similar observations have been reported in references 1,2, 4, 8,15.We have "purified" this experiment by controlling the proportion between the covered and free surfaces of the film supporting liquid. This was achieved by feeding continuousIy one liquid over the surface of another one into which it dissolves; the steady film thus formed covers only a determined fraction of the supporting liquid surface dependent on the flow rate of the liquid fed. THE EXPERIMENTAL ARRANGEMENT (FIGURE 1)In all experiments the film supporting liquid (tap water*) was contained in a prismatical transparent, open dish 300 mm. by 300 mm. by 80 mm. The liquid to be dissolved is allowed to flow over the supporting liquid surface from a glass capillary ( D = 1.2 mm.; I.D. = 0.6 mm.) placed immediately aboveNo differences have been obsesved by using water dist...

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