INVESTIGATION OF REACTIONS OF SIMPLE MAGNESIA SPINELS WITH ALKALINE EARTH ORTHOSILICATES IN THE SOLID STATE *

The spinels MgO Al₂O₃, MgO Cr₂O₃., and MgO Fe₂O₃ and the orthosilicates 2MgO SiO₂, 2CaO SiO₂, 2SrO SiO₂, and 2BaO SiO₂ were synthesized by solid-state reaction of the component oxides or compounds yielding the oxides on ignition. Each of the spinels was tested at various temperatures with each orthosilicate in turn by placing a pellet of each in contact and also by intimately mixing the two. Petrographic microscopy and X-ray diffraction were employed in the identification of reaction products.