Abstract
Oxidation and reduction of Cr(III) species originating from dissolution of Cr2O3 in cryolite-based melts at 900 {degree sign}C was studied. The molar ratio n(NaF)/n(AlF3) was 1.4, which allowed us to perform measurements at the temperature of 900 {degree sign}C. It was found that Cr(III) can be oxidized to Cr(VI) both chemically by oxygen present in the air and electrochemically when using an inert anode. When a carbon anode was used, the formation of Cr(VI) species was not observed. The solubility of Cr(VI) species in the above-mentioned melt was found to be (1570 {plus minus} 16) ppm. Cr(II) species were prepared in situ by the reduction of Cr2O3 with chromium powder. It was found that saturation was achieved after several hours, the concentration of Cr(II) being (239 {plus minus} 14) ppm.
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