An analytical method is given for determining the distribution of cation valencies in MntFes-10.1 for o -: t < : 1.5 at 240". based on the assumption that the existence of only FeZb, Fe3+, Mn2+ and Mn3* is possible and that no change in the equilibrium of the valencies occurs during rapid dissolution. The results are given for t = 0.50, 0.75, 1.00, 1.25 and 1.50. It is shown that near t = 1 the cations Mn3+ and Fez+ are present simultaneously: The formula of manganese ferrite is found to be with a possible error of i 0.025 in the cationic ratio numbers.In addition the temperature dependence of the valence distribution is discussed.I. Introduction Many authors 1 have given their explanation of the anomalous inversity of manganese ferrite, being 0.18 or expressed in the formula (Mn0.82 Feo.18) [Mno. 18 Fe1.8~104, according to neutron diffraction studies2. 3. ] octahedral sites in the close-packed oxygen matrix of the spinel structure. For most of the spinels cations have a marked difference in the (energetic) preference for octahedral or tetrahedral sites. So zinc ferrite has the normal structure (Zn) [Fez] 0 4 , while magnetite is inverse at ordinary temperatures: