Solubility Measurements of Fe₂O₃ and Cr₂O₃ in Fused Na₂B₄O₇-B₂O₃ in Air at 1173 K

Abstract

The solubility of Fe₂O₃ and Cr₂O₃ powder in a binary fused Na₂B₄O₇-B₂O₃ salt system was measured at 1173 K in air. The melt was continuously monitored via a basicity sensor with an oxide ion probe and a zirconia oxygen probe. The basicity of the fused salt was varied from 10.3 to 14.5 by adding B₂O₃ powder to Na₂B₄O₇. For the entire range of the measured basicity, solubility of the Fe₂O₃ was one order of magnitude higher than that of the Cr₂O₃. The solubility of both the Fe₂O₃ and the Cr₂O₃ decreased with an increase in the melt basicity. From the solubility dependence on the melt basicity, both Fe₂O₃ and Cr₂O₃ are expected to dissolve via a basic dissolution reaction.