The oxidizing reaction of some rare-earth chlorides (Pr/CeCl3) in an eutectic (LiCl-KCl) salt was studied by O2 injection. In this study, oxychlorides (REOCl) or oxides (REO2) were formed as reaction products. The results conformed to the thermodynamic equilibrium data calculated by HSC-Chemistry
5.1 software. The conversion ratio of the rare-earth chlorides to insoluble precipitates was over 0.999, after injecting O2 for 7 hours at 650 °C for the eutectic salt temperature.