An investigation of evaporation of lithium

The Knudsen effusion method with mass-spectrometric analysis of evaporation products is used to determine the composition and pressure of saturated vapor over liquid lithium in the temperature range from $627$ to $893$ K. The $\mathrm{Li}(l)=\mathrm{Li}(g)$, $2\mathrm{Li}(l) = \mathrm{Li}_2(g)$, and $\mathrm{Li}_2(g) = 2\mathrm{Li}(g)$ reactions are investigated. The measured values of partial pressure for $\mathrm{Li}$ and $\mathrm{Li}_2$ are used to calculate the values of enthalpy for these reactions at $0$ K by the second, $\Delta_rH^0_0(\mathrm{II})$, and third, $\Delta_rH^0_0(\mathrm{III})$, laws of thermodynamics: $\Delta_rH^0_0(\mathrm{II})=157.9\pm0.5$, $214.2\pm0.6$, and $101.4\pm 1.1$ kJ/mol, and $\Delta_rH^0_0(\mathrm{III})=157.5\pm0.3$, $213.9\pm0.3$, and $101.1\pm0.6$ kJ/mol, respectively.