Studies on the Reactions between Oxides in Solid State at Higher Temperatures. I. The Reaction between Magnesium Oxide and Titanium Oxide

Abstract (1) It has been confirmed that three titanates, i.e., magnesium orthotitanate (2MgO·TiO2), metatitanate (MgO·TiO2) and dititanate (MgO·2TiO2), are formed by the solid reaction between MgO and TiO2; 2MgO·TiO2 is soluble in 4 N HCl and MgO·TiO2 in 12 N HCl, while MgO·2TiO2 is scarcely soluble even in 12 N HCl. (2) By following the course of the reaction analytically, it has been found that the first reaction product is MgO·2TiO2, whatever the mixing ratio of the two components may be; MgO·TiO2 is formed gradually when an excess of MgO is present; and 2MgO·TiO2 is formed similarly, but with difficulty. (3) The reaction has been proved to proceed, under various ex？erimental conditions, in the same manner, and MgO·TiO2 can never be regarded as the first reaction product. (4) The reaction between MgO·TiO2 and TiO2 to form MgO·2TiO2 has taken place more easily than the formation of MgO·TiO2 from MgO 2TiO2 and MgO. (5) It has been concluded that, although there exists a notable rapid initial reaction, a further reaction is controlled by the diffusion of the two components through the reaction product. The energy of activation of the diffusion process of MgO·2TiO2 formation has been estimated to be 36.0 Kilocalories per mole.