Reactivity of lime and related oxides. XI. Production of dolomitic lime

The calcination of dolomite has been studied by determining the changes in specific surface and phase composition and crystallite size during decomposition in vacuo or in air at a series of temperatures up to 900°. The overall surface activities of the dolimes are correspondingly greater than those of the ordinary limes obtained in previous investigations. The calcium oxide crystallites are similar in size to those in ordinary limes, but the magnesium oxide crystallites are much smaller. This is due mainly to the greater volume decrease associated with the magnesium oxide formation. However, this oxide is correspondingly less active than that from magnesite. Hence, some of its sintering is evidently enhanced by the presence of the calcium oxide. At lower temperatures, i.e., below 700° in air, some of the carbon dioxide evolved inhibits the decomposition by recombining with the newly‐formed calcium oxide; this reduces the surface activity of the product. At higher temperatures, the surface activity is also reduced by impurities with lower melting points generally enhancing sintering of the dolime.