Mechanism of decomposition of brucite

Abstract

The inhomogeneous mechanism for the crystallographic transformation of brucite (Mg(OH)₂) to MgO postulated by Ball and Taylor ¹ is re-examined. This postulate was based upon the observation of X-ray reflections attributable to a spinel structure in decomposed brucite crystals. In the present work a relatively pure Mg(OH)₂ powder and Mg(OH)₂ powders containing Fe and Mn were studied. It is shown that the spinel reflections arise from the presence of these impurities and that no spinel phase could be detected (i.e., it is <0.3 %) on decomposition of pure hydroxide. All the observations of Ball and Taylor are satisfactorily accounted for and the experimental basis for the inhomogeneous mechanism shown to be invalid.