AbstractThe elements, Ni, Fe, Cr, and Mn, and their oxides, NiO, Fe2O3, Cr2O3, and MnO2, in a finely divided state, were brought into contact with granular fused MgO in loose form and in pressed disks and also into contact with slabs of high‐fired MgO and BeO. The maximum temperatures reached were 1000°C, 1100°C, and 1200°C in air firings. The degree of reaction was noted by the extent of discoloration of the MgO and BeO near the contact material. Ni showed the least reactivity, Fe and Cr came next, and Mn showed the most reaction. The oxides gave the same order of reactivity, NiO, Fe2O3and Cr2O3, and MnO2, the most. The elements in oxidizing caused more reaction than their oxides in all cases. There was less reaction with BeO than with MgO for corresponding contact material.Firings were also made with these elements and oxides in contact: with pressed disks of fused MgO but in a hydrogen atmosphere. Ni and Fe showed no reaction; Cr, a very slight reaction; and Mn, slightly more reaction. NiO and Fe2O3were reduced to their elements without reaction, whereas Cr2O3did not reduce and gave no reaction. MnO2became semi‐sintered and gave a very slight reaction.Other experiments were made by passing air or N2, dry or through water, into mixtures of granular fused MgO and Mn, MnO2, or Cr, respectively. At 1200°C, reaction was greatest with mo