Reactions in Heated Lime‐alumina Mixtures

Results of heating five lime‐alumina mixtures for 3–120 h. at temperatures from 1045° to 1405° are presented. The mixtures were prepared from mixtures of CaCO 3 (calcite) and α‐Al 2 O 3 and also from co‐precipitated hydroxide gels. Significant departures from equilibrium were noted. In general the gel mixtures approached the equilibrium state more rapidly. Unstable 5CaO,3Al 2 O 3 was not detected. Previous interpretations of X ‐ray diffraction patterns of heated lime‐alumina mixtures are shown to be in error. The mechanism of the reaction cannot be uniquely determined from a study of the bulk reaction products.