Some iron metal used to fabricate crucibles contains impurities comprising manganese, titaium and other elements. Under closed-system conditions these impurities impose an fo 2 that can differ from that of a silicate charge in equilibrium with pure metallic iron. Equilibration of the impurities in the crucible with the charge can reduce the iron oxide component of the charge and contaminate it with manganese and titanium. Pretreatment of impure iron crucibles in a CO 2 -CO atmosphere at 1050 degrees C, under conditions slightly more reducing than Fe-Fe (sub 1-x) O, minimizes undesirable changes in the bulk composition of the charge.--Journal abstract.

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