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Review article

Air/Solution Interface and Adsorption – Solution for the Gibbs Paradox

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

Full text: english pdf 523 Kb

page 381-394

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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

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