Vapor Pressures of TiO(g) in Equilibrium with Ti2O3(s) and Ti3O5(s, β); Dissociation Energy of TiO(g)

The vapor in equilibrium with Ti₂O₃(s) and Ti₃O₅(s, β) at 1720°C was examined with a mass spectrometer equipped with a Knudsen cell high temperature inlet system. With 50‐eV ionizing electrons, the ions TiO⁺, Ti⁺, and ${\mathrm{TiO}}_2^{+}$ were observed. Ionization efficiency curves indicated that Ti⁺ resulted from dissociative ionization of TiO(g). The ions TiO⁺ and ${\mathrm{TiO}}_2^{+}$ resulted from the parents TiO(g) and TiO₂(g), respectively. The intensities of TiO⁺ and ${\mathrm{TiO}}_2^{+}$ over the temperature range from 1675 to 1770°C indicated that P_TiO/PTiO₂=4.06₆. The principal vaporization reaction was $$\text{2\hspace{0.17em}}{\mathrm{Ti}}_2{\mathrm{O}}_3(\mathrm{s}\mathrm{)\; \rightleftarrows }{\mathrm{Ti}}_3{\mathrm{O}}_5(\mathrm{s}\mathrm{,\; \beta )\; +}\mathrm{TiO}(\mathrm{g}\mathrm{).}$$ The vapor pressures of TiO(g) were determined as a function of T by using the Knudsen effusion method. A value of $D_0^{\mathrm{o}}[\mathrm{TiO}(\mathrm{g}\mathrm{)]}$ of $\text{160.82±4.56}$ kcal/mole was determined through a ``third‐law'' analysis of the data. This value is compared with values determined recently through studies of isomolecular reactions. A value for $D_0^{\mathrm{o}}[{\mathrm{TiO}}_2(\mathrm{g}\mathrm{)]}$ of $\text{310.37±2.96}$ kcal/mole was derived.