Equilibrium between (Li,Na,K,Mg)-carbonate melt, gaseous CO2 and MgO

Abstract

Considerable amounts of MgCO₃ may appear in alkali metal carbonate melts in contact with MgO and carbon dioxide gas. The equilibrium between dissolved MgCO₃, MgO and carbon dioxide gas has been studied. The results satisfactorily obey thermodynamic theory based upon a melt model used by Förland for the similar system with CaCO₃ and CaO. Values of the melting point (∼990°C) and for the heat of melting (∼14 kcal/mole) of MgCO₃(at 1 atm CO₂ pressure) have been derived. “Anomalous” results obtained below about 550°C when heating clear (Li,Na,K,Mg)-carbonate melts (under carbon dioxide) are attributed to the appearance of an “active” form of MgO. Some data on the quaternary system Li₂CO₃+Na₂CO₃+K₂CO₃+MgCO₃ have been obtained. MgO is not “inert” against molten alkali metal carbonates under appropriate conditions.