Behaviour of Lux bases in ionic melts

The investigation of the equilibria occurring in the dissociation processes of oxide ion donors (Lux bases) in ionic melts is of great practical importance 

Regarding the above dissociation reactions, it should be noted that the process of BaO dissociation results in the accumulation of foreign Ba2+ ions in the melts this, in turn, changes the chemical properties of the melt-solvent. Also, BaO possesses a limited solubility in molten alkali metal halides and its dissociation is essentially incomplete even in unsaturated solutions. Even if we neglect the incomplete dissociation, there are other limitations on the practical use of this base for studying oxoacidic properties of ionic melts. It cannot be used in the following cases  

Oxygen electrodes in ionic melts. Oxide ion donors 

The behaviour of carbonates, hydroxides and peroxides in ionic melts should be considered separately. 

The matter consists in the fact that although alkali metal hydroxides are classified among strong bases, they are nevertheless distilled without decomposition at temperatures near 1300 °C. Sodium and potassium carbonates melt without decomposition at 854 and 890 °C, respectively, and the partial pressure of C02 over the said melts is low enough even at 1000 °C. Thermal dissociation of Na202 starts at temperatures close to 460 °C, whereas K202 melts without appreciable decomposition at 490 °C [114, 121]. Hence, these bases should be sufficiently stable under the experimental conditions provided in most experimental oxoacidity studies (200-800 °C). 

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