STRUCTURAL TRANSITIONS IN VICINAL WATER - PORE-SIZE AND TEMPERATURE-DEPENDENCE OF HEAT-CAPACITY OF WATER IN SMALL PORES

The temperature dependence of the heat capacity of vicinal water has been measured in 40-, 140-, and 242-angstrom silica pores. The data are discussed in light of measurements of other physical properties of vicinal (interfacial) water and a statistical thermodynamic model proposed by Etzler. Notable heat capacity "spikes" were found to be superimposed on a linearly increasing trend of heat capacity with temperature. These spikes were observed near the same temperatures where Drost-Hansen found other evidence for the existence of vicinal water structure transitions. The position and size of the heat capacity spikes to not appear to vary significantly with pore size. Physiological anomalies have also been observed near these "Drost-Hansen temperatures".