Thermal decomposition of barium perchlorate

Abstract

The thermal decomposition of anhydrous barium perchlorate to barium chloride and oxygen has been studied by pressure measurements, or by weight loss, in vacuo, under the accumulated gaseous products (0–3 Torr oxygen), under dry air or nitrogen, and mixed with added barium chloride. The plots of fractional decomposition (α) against time (t) are complex, as would be expected for a reaction proceeding via unstable intermediates. The most pronounced features of the α(t) curves are an initial acceleratory period, which is succeeded by an approximately linear period and then, after a sharp break (reduction in rate), by a deceleratory period which conforms to the contracting-volume kinetic law. The latter stage is associated with the decomposition of barium chlorate and has an activation energy of 59 kcal/mole. The first two stages comprise the decomposition of perchlorate to chlorate with the approximate stoichiometry 3ClO4− = 2ClO3− + Cl− + 3O2. A chain reaction sequence, which involves O atoms as chain carriers, is proposed for these stages. The effect of the removal of products, of increasing the ambient pressure of inert gas, and of the addition of barium chloride, can all be explained on this model.