The reactions of anhydrous MgSO4 and MgCl(2)fferent molten nitrates and nitrites which produce fine MgO powders were studied. The stoichiometries of the reactions were established and the effects of various reaction conditions on the properties of the MgO powders produced were investigated. The addition of Lux-Flood bases to nitrate melts can lower the reaction temperatures and further lower the crystallite size of the MgO powders produced. The results showed that very fine MgO powders with high purity can be precipitated from molten nitrates and nitrites at temperatures below 600 degrees C, and these powders can be obtained with soft agglomeration if the powders precipitated are properly processed.