Mass spectrometric study of the vaporization of lithium metasilicate

The vaporization of Li₂SiO₃(c/1) has been studied by the mass spectrometric Knudsen effusion method. The vaporization process has been found to be incongruent. Partial pressures of Li(g), LiO(g), Li₂O(g), SiO(g) and Li₂SiO₃(g) over Li₂SiO₃(c/1) have been determined in the temperature range 1166–1762 K. Partial pressures of O₂(g) have also been calculated from the reaction Li₂SiO₃(1) = 2 Li(g) + SiO(g) + O₂(g). The enthalpies of formation and the atomization energies for LiO(g) and Li₂O(g) have been evaluated from the partial pressures to be ΔH^o_f0(LiO,g) = (84.5 ± 12.8)kJ/mol, ΔH^o_f0(Li₂O, g) = (?148.1 ± 15.8)kJ/mol, D₀^o(LiO) = (321.4 ± 12.8)kJ/mol and D₀^o(Li₂O) = (713.2 ± 15.8)kJ/mol, respectively. The value of D₀^o(Li₂O) is somewhat greater than twice that of D₀^o(LiO).