Relative adsorption isotherms of 2,5-lutidine from the preferentially wetting water-rich phase beta to silica have been measured at numerous temperatures between T-c (critical temperature of the liquid mixture) and T-w (wetting transition temperature in the diphasic Liquid) and integrated versus chemical potential to obtain surface tensions between solid and liquid, Delta sigma(sl). Extrapolation of both types of curves to the phase separation point makes it possible to compare data along the coexistence curve with a theoretical model. The divergence of the adsorption data at T-c, but not at T-w, is consistent with wetting behavior and is partially what could be expected from theory : the experimental adsorption enhancement can be identified by the critical behavior of the surface of a preferentially wetting bulk phase. However, the sign of adsorption is different from the sign found from most of the theoretical sample models. Surface behavior in the adsorption and surface tension is thus partially proved, experimentally, to depend on wetting properties of the studied Liquid phase in the diphasic and probably on the nature of the wetting transition.