THE MELTING OF UNSATURATED CAPILLARY CONDENSATE

In many adsorbed systems, heat capacity peaks have been observed to oc cur near the triple-point temperature of the bulk adsorbate. These pea ks are now understood to be due to the melting of unsaturated capillar y condensate. In this paper we study that phase transition, presenting new data for these peaks in CH4, Ar, and Kr adsorbed in graphite foam , and analyzing those data in terms of competing models of melting of capillary condensate. We conclude that capillary condensate melts alon g a curve in the temperature-chemical potential plane that may be pred icted from the properties of the bulk adsorbate, independent of the na ture of the substrate.