Carbonate ions in LiCL-Li2O salt are a source of carbon contamination in the electrolytic refining of metal oxides, and their concentration is also an essential information for understanding the CO2 decomposition process. In this study, the solubility of gaseous CO2 in molten LiCI-Li2O was studied with the goal of developing processes to decompose the oxides effectively. Ar-CO2 gas mixtures were dissolved in molten salts containing various amounts of Li2O, and the solubility of the CO2 gas was calculated by measuring the mass difference between the molten salts before and after the CO2 dissolution. The molar amount of dissolved CO2 gas was almost as large as the molar quantity of Li2O when the partial pressure of CO2 was 1.0 or 0.5 atm for Li2O concentrations in the range of 0-60 mol%. This confirms that a large quantity of the oxide ions reacted with the CO2 gas, resulting in the generation of carbonate ions. (C) 2014 Published by Elsevier B.V.