Air-Solution Interface and Adsorption – Solution for the Gibbs ParadoxReport as inadecuate

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Croatica Chemica Acta, Vol.80 No.3-4 November 2007. -

Several experimental evidences differentiating an insoluble monomolecular film just on the air-

water interface from an adsorbed film of soluble amphiphile solution are presented in order to

suggest that the adsorbed film is not located at the air-solution interface. The difference between

the two films can be observed by evaporation rates of water across the air-solution interface

of three kinds of surfactant solutions and across an insoluble film or monolayer, by the

corresponding activation energies, and by the kinetic theory of evaporation across the air-solution

interface. The difference was further substantiated by the Brewster angle microscopy,

BAM, image of the air-water interface. Surface tension vs. concentration curve for soluble surfactant

solution was divided into three regions to solve the Gibbs paradox, and then the adsorbed

film turned out to be concentrated as aggregates at some distance beneath the air-solution

interface. The new concept of adsorbed film is consistent with several interfacial phenomena

of surfactant solutions.

interface; adsorption at the air-solution interface; interfacial tension; evaporation rate of water; BAM image

Author: Yoshikiyo Moroi - ; Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan



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