A thermodynamic investigation of dilute solutions of hydrogen in liquid Li-Pb alloys

Isothermal measurements of hydrogen decomposition pressure (P) vs. hydrogen concentration (Xsub(H)) were carried out on ten Li-Pb alloys in the composition range 0.1 <= X sub(Pb) <= 0.8. Each alloy was investigated at several temperatures from 50 to 400 K above the corresponding liquidus point and at hydrogen pressures up to 15 kPa. Sieverts' law (√P = KXsub(H), as Xsub(H) -> 0) was found to be obeyed under these conditions. The Sieverts' constants showed a 105-fold increase as the Pb content was increased over the stated composition range. The lnK vs. Xsub(Pb) data, fitted to a thermodynamic model, yielded a semi-empirical equation which produced (1) Sieverts' constants within the measured temperature and composition ranges, (2) an inflection point at Xsub(Pb) approx.= 0.3, presumably caused by the formation of partly ionic Li-Pb bonds, (3) a steady decrease in the temperature coefficient as a function of Xsub(Pb), resulting in a sign reversal at Xsub(Pb) approx.= 0.6, and (4) Sieverts' constant estimates for pure liquid lead. Availability of the latter estimates permitted testing of three statistical mechanical models against the experimental data. The results were compared with other literature on the H-Li-Pb system. (orig.)