Reduction of Enthalpy of Fusion and Anomalies during Phase Transitions in Finely Divided Water

Abstract

Solid-liquid phase transitions in finely divided water (FDW) obtained by the adsorption of vapor on large silica surface have been studied with differential scanning calorimetry (DSC). Large reduction of both freezing $\ensuremath{\Delta}{H}_{f}$ and melting $\ensuremath{\Delta}{H}_{m}$ enthalpies with decreasing the adsorbed weight has been observed. A model for the water/silica system, in which a reduced amount of adsorbed water gives rise to a smaller size of microdroplets, is introduced to explain the reduction of $\ensuremath{\Delta}{H}_{f}$, $\ensuremath{\Delta}{H}_{m}$, and other anomalies during the phase transitions in FDW.