Sensitive Determination of Oxygen Solubility in Alkali Carbonate Melts

The solubility of in Li-K and Li-Na eutectic carbonate melts has been estimated in the range 600-700°C using a highly precise chemical titration method. In general, oxygen solubility is found to be distinctly higher in the Li-K than in the Li-Na eutectic with a tendency for such a solubility difference to disappear at 600°C. The precise determination of solubility values at different and partial pressures allowed evaluation of plausible oxygen dissolution mechanisms by a data fitting procedure. Our results support the assumption of a predominant superoxide formation at 650 and 700°C in both melts, with the difference that in Li-Na carbonate oxygen appears to dissolve also through formation of peroxymonocarbonate ions. At 600°C, molecular oxygen is found to be the major oxygen component.