Mass spectrometric investigation of the dissociation energy of the molecule AlAu and estimated bond energies of some diatomic intermetallic compounds with gold

High‐temperature Knudsen‐cell mass spectrometry has been used to measure the gaseous equilibria over an aluminum‐gold or aluminum‐silver‐gold alloy in a tantalum cell. The enthalpies for the reactions (1) $\mathrm{AlAu(g)\; =\; Al(g)}+\mathrm{Au(g)}$ , and (2) $\mathrm{AlAu(g)}+\mathrm{Au(g)}={\mathrm{Au}}_2(\mathrm{g}\mathrm{)\; +}\mathrm{Al(g)}$ were measured. The following dissociation energy D°₀, heat of sublimation ${\mathrm{\Delta \; H°}}_{\text{s,298}}$ , and heat of formation ${\mathrm{\Delta \; H°}}_{\text{f,298}}$ were derived from these reaction enthalpies for gaseous $\mathrm{AlAu}\text{: 77.0 ± 1.5,\hspace{0.17em}98.4 ± 2.5,\hspace{0.17em}}\mathrm{and}\text{\hspace{0.17em}88.9 ± 2.0\hspace{0.17em}}{\mathrm{kcal\; mole}}^{\text{−1}}$ , respectively. The dissociation energy of AlAu(g) has been interpreted in terms of the Pauling model of a polar bond. This model has been used to calculate dissociation energies of selected intermetallic compounds between transition metals, Group III metals, and Group IV metals with gold, which are compared with available literature data.