Freezing has been detected in the adsorbed water and benzene of porous Vycor glass a t temperatures below that a t which the bulk phases freeze. The evidence presented by equilibrium pressure measurements and dimensional changes of the systems is considered in terms of theories of capillary condensation and freezing in cements and soil. Although not all the results can be esplained, it is concluded that the freezing process is a gradual one for both adsorbate-adsorbent systems. The evidence further suggests that hysteresis is absent in isotherms if the solid phase has formed.

A new technique is described for detecting possible phase transitions of adsorbates. The method i~ivolves the measurement of length changes of the solid, but only solids for which the surface-to-volume ratio is large could be used with the present form of instrument because of its moderate sensitivity. Using this measurement an apparent phase transition for water adsorbed on porous Vycor glass has been detected a t approsirnately -22' C.The detection of phase changes occurring in adsorbates 011 solids has been attempted in a variety of ways. Among these are the dependence of equilibriuili pressure 011 teillperature, the anomalies of carefully deterillined cooling curves, and dilatoinetric techniques (1, 2, 3). The experimeiltal evidence is not always readily acceptable because of the methods employed.Recently Puri, Siilgh, and i\/Iyer (4) reported the experi~neiltal detection of the forrnation of the "solid" phase for a variety of adsorbate-adsorbent systeins by means of measure~neiits of equilibrium pressures. These authors compared their data with predicted freezing point depressions based upoil the I

No abstract