Effect of dilute silica gel on phase separation of a binary mixture

We report the results of an experimental study of the effect of a dilute silica network on critical phenomena in a binary mixture of 2,6-lutidine and water. Light-scattering measurements of this sytem show that its structure does not differ significantly from that of the gel, but that the scattered intensity increases dramatically as the two-base region is approached. We interpret these results in terms of a layer of lutidine-rich fluid adsorbed in the silica surface and the resulting changes in concentration of the nonadsorbed fluid. © 1991 The American Physical Society.