Magnesium oxide in aqueous suspension is hydrated by the "via solution" mechanism. In the initial stage, there arise brucite nuclei on active centres of the surface of MgO, and this is associated with a rapid increase in the specific surface area of the solid phase. In the subsequent stage, the specific surface area decreases as a result of a slowing down of the nucleation rate, probably due to inactivation of the free active centres that become overgrown by the forming brucite crystals. The time course of the entire process is described by the equation ln (1/(1-y)) = (kt)n; where y is the rate of conversion, t is time, k is the rate constant and n is a constant of the empirical equation, having the value of 2/3. The temperature dependence of the rate constant conforms to the Arrhenius equation and has the activation energy E = 54.7 kJ mol-1.
