Purification of halide ionic melts from oxide-ion admixtures

2 Purification of halide ionic melts from oxide-ion admixtures 

Novozhilov et al. studied the solubility of HC1 in molten alkali- and alkaline earth metal chlorides [268, 269] and found the solubility of HC1 in these melts to obey Henry s law. The thermal dependences of the solubility (the Henry coefficient values) of HC1 in molten alkaline earth metal chlorides, which are exposed to the pyrohydrolysis, are presented in Fig. 2.5.3. The dependences are close to linear anOd their treatment by the least-squares method allows the calculation of the thermodynamic parameters of HC1 dissolution in the chloride melts. These values are presented in Table 2.5.2. 

A comparison of the entropy values with those of dissolution of argon and C02 in molten fluorides [270] shows that they are very close. This means that the process of HC1 dissolution in molten chlorides runs according to the physical mechanism, i.e. the dissolved molecules occupy voids in the melt structure. A small reduction in the gas solubility on moving from CaCl2 to BaCl2 melts is explained by an increasing surface tension in the said sequence of molten halides. 

The dissolution process of HC1 in molten alkali metal halides is accompanied by the formation of H-bonds, whose energies (kJ mol-1) increase in the sequence Na (21.9)—K (25.1)—Rb (27.2)—Cs (31.0) [269]. The strength of H-bonds in molten chlorides is dependent on the polarizing 

Oxygen electrodes in ionic melts. Oxide ion donors 

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