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Studies the prewetting transition in the silica-water-2,5-dimethylpyridine system through adsorption isotherms. Universality of the wetting phenomena; Description of the physical properties.

Examines the phase change possibilities in the surface phase formed in a binary liquid system in contract with a solid on the basis of adsorption isotherms. Layering in surfaces as a phase surface change leading to condensed phase from a gaslike one; Packing effects in liquid mixtures.

The wetting behavior of the water–2,5 lutidine system has been studied around the lower consolute point (Tc=13.1 °C). We have measured contact angles and surface tensions by varying the concentration and temperature. In the diphasic region, a wetting transition has been observed at 46–47 °C on a silica wall by direct observation of the solid–liquid–liquid contact angle. The perfect wetting occurs close to Tc, the wetting phase is water rich. At the liquid–vapor interface, the analysis of the values of the surface tensions shows that, close to Tc, they obey critical laws and that a lutidine rich phase perfectly wets the vapor and the water rich phase. These behaviors have been analyzed on the basis of the contact angles of the monophasic on a silica wall on both sides of the coexistence curve, and the general variation of the surface tensions. A second wetting transition has been shown on a differently washed glass surface. Reference is made to the theoretical and experimental works following the early work of Cahn. [ABSTRACT FROM AUTHOR]

Experimental data of surface tensions along the critical isochore (1) and the two branches of the coexistence curve (2,3) for the water-2,5 lutidine system have been used in order to check signs and values of the universal amplitude ratios of the critical laws in the forms σα,j=σc+A(T-Tc)+Bj(T-Tc)μ, j=1,2,3, with imposed μ=1.26. A and the Bj’s being highly correlated, several statistical tests using the values of the ratios have been used. Experimental values are compatible with P+=B/Bi=-0.59 (B: isochore; Bi: interfacial tension in the two phases system), maybe with Q=B/B‘=-0.83 (B‘ one branch of the coexistence curve) and certainly with its sign. The other ratios cannot be verified at all by the experimental data. [ABSTRACT FROM AUTHOR]