Solubilities, and solution and solvation enthalpies, for nitrogen and hydrogen in liquid lithium

Abstract

The solubilities of nitrogen and of hydrogen in liquid lithium have been determined up to 2.77 mol% N and 5.68 mol% H by electrical resistance methods, and they can be represented, in part, by the equations log 10x N = 1.168 − 2036 T 473 < T < 708 K log 10x H = 1.523 − 2308 T 523 < T < 775 K where x is the solute mole fraction. The results show that the nitrogen and hydrogen content of lithium can be reduced to 0.08 and 0.03 mol%, respectively, by filtration at 200 °C. Solubilities provide values of the partial molar enthalpies, H ( soln) , and entropies, S ( soln) (with respect to the precipitating phase), of solution of 39.23 kJ mol −1 and 22.35 J K −1 mol −1 (for Li 3N), and 44.18 kJ mol −1 and 29.15 J K −1 mol −1 (for LiH). The values of H ( soln) are used to derive solvation enthalpies of −3473 and −427 kJ mol −1 for nitride and hydride ions, respectively, in the metal. The hydrogen solubilities augment the liquidus of the Li-LiH phase diagram.