Thermodynamics of iron oxide in Fe sub x O-dilute CaO+Al sub 2 O sub 3 +Fe sub x O fluxes at 1873K

The distribution of iron between Fe sub x O-dilute CaO+Al sub 2 O sub 3 +Fe sub x O fluxes and Pt+Fe alloys, and the redox equilibrium of iron ions in these fluxes, was experimentally investigated in pressure-controlled CO sub 2 /CO gas at 1873K. Total iron content in flux (%Fe exp T ) and the ratio of (%Fe exp 2+ ) to (%Fe exp T ) in fluxes with constant X sub CaO /X sub Al2O3 ) can be related to the activity of iron, alpha sub Fe , and the partial pressure of oxygen, rho sub O2 , using the following equation: (TFe exp T )={(C sub Fe2+ ) rho sub O2 exp 1/2 +(C sub Fe3+ ) rho sub O2 exp 3/4 )} alpha sub Fe , (%Fe exp 2+ )/(%Fe exp T )=1/1+{(C sub Fe3+ )/(C sub Fe2+ )}x rho sub O2 exp 1/4 , where C sub Fe2+ and C sub Fe3+ are the ferrous and ferric ion capacities, respectively, defined as C sub Fe2+ =(%Fe exp 2+ )/ alpha sub Fe rho sub O2 exp - 1/2 , C sub Fe exp 3+ =(%Fe exp 3+ ) / alpha sub Fe rho sub O2 exp 3/4 . The present article applies these parameters to the evaluation of the activity coefficient of Fe sub x O at infinite dilution, gamma sub FexO exp o , relative to the liquid iron oxide in equilibrium with iron. Furthermore, the composition dependence of gamma sub FexO exp o is discussed.