Capillary Condensation due to van der Waals Attraction in Wet Slits

Wetting films (of thickness t≤14 nm) of t-butanol in slits of mica have been studied as a function of the slit width H. A capillary condensation transition occurs when H≈3t for t>5 nm. This is consistent with a mechanism of film thickening and coalescence due to van der Waals forces across the slit. van der Waals thickening cannot account for the transition with thinner $t<5$ nm) adsorbed films, as found previously with nonwetting liquids.