Abstract The reactions of four manganese compounds with molten lithium nitrate-potassium nitrate eutectic were studied. Manganese(II) chloride and manganese(II)-sulphate reacted to give manganese dioxide, the reaction being quantitative above 350°. Potassium manganate(VI) disproportionated to give permanganate, a potassium manganate(IV) and free oxide ions. The permanganate formed then reacted more slowly, the final products of manganate(VI) being oxygen and a manganate(IV) containing the lithium cation predominately. Pure potassium permanganate reacted to give oxygen and a manganate(IV) of different stoichiometry but again largely as the lithium salt.