Oxidation State of Chromium in CaO–Al 2 O 3 –CrO x –SiO 2 Melts under Strongly Reducing Conditions at 1500°C

Equilibrium ratios Cr 2+ /Cr 3+ of chromium oxide dissolved in CaO–chromium oxide–Al 2 O 3 –SiO 2 melts have been determined by analysis of samples equilibrated at 1500°C under strongly reducing conditions ( p o2 = 10 −9.56 to 10 −12.50 atm). The majority of the chromium is divalent (Cr 2+ ) under these conditions and Cr 2+ /Cr 3+ ratios at given constant oxygen pressures decrease with increasing basicity of the melts, expressed as CaO/SiO 2 ratios. In addition, Cr 2+ /Cr 3+ ratios, at a given CaO/SiO 2 ratio, are relatively unaffected by the amount of Al 2 O 3 present.