Reaction of oxygen and oxygen containing gas mixtures (Ar–O2, O2–H2O, Ar–O2–H2O of various compositions) with chloride melts containing uranium(III) ions was studied. The experiments were conducted in molten LiCl at 750°C and LiCl–KCl eutectic mixture at 550 and 750°C. Concentration of uranium in the melt varied from 0.3 to 3.5 wt %. The effect of oxygen to uranium molar composition and gas mixture composition on degree of uranium precipitation from the melt and composition of the reaction products was investigated.