| Popis: |
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 Forland 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+Na2CO 3+K2CO3+MgCO3 have been obtained. MgO is not "inert" against molten alkali metal carbonates under appropriate conditions. |
