抄録
Activities of NaO0.5 and Na(CO3)0.5 in Na2O-CO2-Sb2O5 melts were determined at 1423-1523 K by the EMF method, using beta″-alumina as a solid electrolyte, over the composition range N≥0.7{=nNa2O⁄(nNa2O+nSb2O5), n: the number of moles} under various partial pressures of CO2. The activity of SbO2.5 was calculated from the activity of NaO0.5 by integrating the Gibbs-Duhem relation. The partial pressure of CO2 has great influence on the activities of the components in the system. The existence of a liquid state miscibility gap was suggested in the Na2CO3-rich composition range. The solubility of CO2 in the melts was also measured at 1523 K. The results of the solubility measurements of CO2 imply that Na2CO3 is decomposed according to the stoichiometric reaction corresponding to the formation of Na3SbO4 species in the melts, and, therefore, the activity of Na3SbO4 was also discussed.
