Vapor Species of the Barium-Oxygen System

Abstract

Mass-spectrometric and vacuum-thermobalance studies of barium oxide between 1365° and 1917°K yield for the equilibrium pressure of BaO gas, logPatm = − 22610 / T + 7.90. The enthalpy for the reaction BaO(a) = BaO(g) was calculated to be ΔH°298 = 110.9 ± 2.8 kcal / mole by the second-law method. The third-law date are consistent with this value if a 3Π state is assumed to be at or near (within a few hundred cm−1) the ground state of BaO(g). The heat of sublimation of the dimer Ba2O2(g) was found from the mass-spectrometer study to be about 142 kcal/mole and the heat of the reaction BaO(g) + Ba(g) = Ba2O(g) was found to be − 73 ± 15 kcal/mole at 1800°K. No reaction of barium oxide at 1800°K with O2(g) at pressures up to 10−3 atm was detected.