Oxoacidity reactions in molten LiCl + KCl eutectic (at 470 °C): potentiometric study of the equilibria of exchange of O2-between Al(III) systems and carbonate and water systems

Abstract

The reactions between aluminium chloride and oxide anion were studied in molten LiCl+KCl eutectic at 470°C. For that purpose, a pO 2− indicator electrode made with a membrane in yttria-stabilized zirconia has been used and tested by means of a carbonate ion whose dissociation constant, 10 −2.15 atm, was determined. Then, the electrode has allowed us to obtain the formation constant of AlO + (solvated by Cl − ) and the solubility product of Al 2 O 3 ( S ): 10 10.7 and 10 −27.4 , respectively (molality scale). The equilibrium constant of the following system: 2HCl (g)+O 2− agH 2 O (g)+2Cl − has also been determined: 10 −9.93 atm mol kg −1 . The conditional solubility of alumina in LiCl+KCl melt is discussed.