Critical and wetting transitional adsorption behaviour in a liquid system against vapour and other walls

The adsorption of 2, 5 DMP (2, 5-dimethylpyridine) at the free surface of w ater (1)-2, 5 DMP (2) liquid mixtures was determined from surface tension a nd activity measurements. Two divergences were found: the former was observ ed at T-c for the critical isochore and the 2, 5 DMP-rich gamma -phase whic h, at coexistence, completely wets the surface at T-c, whereas the latter w as noticed at T-c for the water-rich beta -phase. These results were compar ed with those found under similar conditions for the same liquid system wit h silica as the wall; this comparison is quite fruitful because, with silic a, the preferentially wetting phase is the beta -phase.