PROPERTIES OF CACL2 HYDRATE WITH AN INORGANIC POWDER .2. MELTING BEHAVIOR AND THERMODYNAMIC PROPERTIES OF CACL2.NH2O(N = 6.00-7.35) WITH ALPHA-AL2O3 OR ALPHA-SIC POWDER

The melting behaviour of CaCl2.nH2O (n = 6.00 and 7.35) coexisting wit h two powders, alpha-Al2O3 and alpha-SiC, has been investigated by dif ferential scanning calorimetry (DSC). With alpha-Al2O3 powder and CaCl 2.6.00H2O, the melting point of the hydrate and the molar enthalpy of melting decreased as the water content decreased and the specific surf ace area of the powder increased. The observed melting point correspon ded to the transition point shown by the electrical conductivity. With alpha-SiC powder and CaCl2.6.00H2O, the melting point and molar entha lpy of fusion for the hydrate were constant over the range 17.2-48.0 v ol.% hydrate content. These observations led to the conclusion that th e phase transition of the hydrate near the surface of the solid phase was significantly influenced by the hydrophilicity of the surface of t he powder.