BET Modeling of Solid–Liquid Phase Diagrams of Common-Ion Binary Salt Hydrate Mixtures. II. Calculation of Liquidus Temperatures

Abstract

The BET method, according to which a molten salt hydrate is considered as if the water is “adsorbed” on “sites” of the salt, was used to model the liquidus temperatures of binary mixtures of common-ion salt hydrates. The method requires as input the BET parameters r, the number of sites and ε, the energy of adsorption in excess of that of the condensation of water vapor, as derived in the preceding paper. Further needed input information is the melting temperature of the salt that crystallizes out and its latent heat of melting. It is possible to model the liquidus temperature of the branch of the phase diagram between the pure salt that crystallizes out and the (first) eutectic encountered in the system with this input. The method was applied successfully to binary salt hydrate systems involving magnesium nitrate with magnesium acetate and with aluminum or nickel nitrates, magnesium and nickel chlorides, and calcium chloride with its bromide and nitrate, and with magnesium nitrate.