KINETICS OF HYDRATION OF MAGNESIUM-OXIDE IN AQUEOUS SUSPENSION .2. THE EFFECT OF CONDITIONS OF FIRING BASIC MAGNESIUM CARBONATE ON THE SPECIFIC SURFACE-AREA OF MAGNESIUM-OXIDE

Thermal decomposition of basic magnesium carbonate (4MgCO3.Mg(OH)(2).4 H(2)O) yields porous pseudomorphoses of the the original crystals. The specific surface area of the oxide decreases exponentially with incre asing firing temperature. The maximum specific surface area of MgO fir ed at 500 degrees C amounts to 155 m(2)g(-1), falling down to 20 m(2) g(-1) when fired af 1200 degrees C. Extension of the lime of firing af fects negligibly the specific surface area. Of the admixtures accompan ying magnesium oxide in dolomitic raw materials, the specific surface area of fired magnesia is mostly affected by ferric oxide. Under the s ame firing conditions, at a content of 2 wt. % of this component, the specific surface area decreases down to one tenth of that of non-doped magnesium oxide.