PHASE TRANSITIONS OF ADSORBATES: 1. SPECIFIC HEAT AND DIMENSIONAL CHANGES OF THE POROUS GLASS – WATER SYSTEM

Abstract

The specific heat and dimensional changes of the porous 96% silica glass – water system were measured simultaneously between −35 °C and +2 °C with coverages of 1.6, 4.0, 5.3, and 7.7 molecular layers. The specific heat of the adsorbate below the transition range was found to be higher than that of ice. No phase change was detected with the lowest concentration. At the higher coverages, transition always occurred near −9.5° and was of the anomalous first order type. The values of the specific latent heat of fusion, calculated by assuming that two monolayers do not freeze, are 49.4, 54.4, and 55.5 calg−1, depending on the concentration. The correlation between the results of calorimetric and dimensional change measurements was considered satisfactory.