Reactivity of lime and related oxides. I. Production of calcium oxide

The calcination of calcium hydroxide and of calcium carbonate (precipitated or prepared from calcium oxalate monohydrate) has been studied by determining the changes occurring in the specific surface and lattice structure during each decomposition in vacuo or in air at a series of temperatures up to 900° or 1000°c. In parallel with earlier observations on calcium hydroxide, the decomposition of the calcium carbonate results in a several‐fold increase in specific surface which is ascribed to the activation of the newly‐formed calcium oxide when it recrystallizes from a pseudo‐lattice of calcium carbonate to very small individual crystals having a more stable lattice structure. The preliminary decomposition of the calcium oxalate, particularly in vacuo at about 450°, produces samples of calcium carbonate of much higher specific surface than that of the precipitated form, but they tend to sinter considerably at higher temperatures before decomposing to calcium oxide. Further calcination after complete decomposition always causes sintering of the calcium oxide, the extent of which is enhanced by increased temperature whether in vacuo or in air.