Calcium Carbonate Decomposition in Carbon Dioxide Atmosphere

Abstract

Calcite crystal fragments of known surface area were decomposed in controlled carbon dioxide atmospheres. The decomposing sample was weighed continuously on an automatically recording thermobalance and a rate of weight loss per unit area was obtained. A rate expression involving actual and equilibrium CO 2 pressures and the decomposition rate in pure nitrogen was derived. The mechanism of the decomposition is pictured as being a two‐stage phenomenon. Initially the CO 2 leaves the CaCO 3 cell and the residue of the CaO apparently assumes a metastable rhombohedral configuration similar to the original CaCO 3 . The second step of the reaction is the formation of well‐crystallized CaO from the active CaO. The active CaO thus acts as a bridge for this reversible reaction.