The limits nαmax and nβmin of the two‐phase region of PdHn can only roughly be estimated from the shape of the equilibrium isotherms pH2(n). Other methods applied so far do not yield more accurate results. More precise values can be obtained, however, from measurements of the magnetic susceptibility x as a function of the hydrogen content n at various temperatures. Such x(n) isotherms have been measured at temperatures between 20 and 300°C and H2 pressures up to 140 atm (0 · n · 0.8), using samples of Pd wire (1 mm) and Pd foil (33 μm). In the homogeneity range isotherms for adsorption and desorption were identical, in the two‐phase region, however, hysteresis was always observed. Here the desorption curve was taken as the equilibrium isotherm, and was applied to determine the values of nαmax and nβmin by extrapolation. Measurements on Pd black in the same region of pressure and temperature showed a number of peculiarities, for instance smaller values of susceptibility and smaller hysteresis loops as compared with bulk Pd. These can be attributed to the large specific surface area of Pd black as well as to its strongly distorted lattice structure. By means of the measurements on bulk Pd the position of the critical point of the palladium‐hydrogen system could be redetermined with rather high precision: Tc = 291 ± 2°C; nc = 0.250 ± 0.005 mol H/mol Pd; Pc = 19.7 ± 0.2 atm H2. The measurements on Pd‐black yielded within the limits of error the same values for the critical temperature and the critical pressure, whereas the value of the H/Pd ratio, properly corrected, was found to be a bit higher, namely nc = 0.260 ± 0.005.

Die Grenzen namax und nßmjn des Zweiphasengebietes von PHn können aus der Form der Gleichgewichtsisothermen pHz (n) nur grob abgeschätzt werden.

An evaluation for the paramagnetic susceptibilities of Pd/Fe and Pd/Fe/H alloys is proposed which accounts for the filling of the bands by electrons from the iron atoms. The susceptibilities are split into a "band" and an "iron" contribution, the latter of which exhibits Curie-Weiss behavior. Reevaluation of Gerstenberg's data yields a magnetic moment of 5.9 μB per iron atom. For hydrogenated Pd/Fe alloys the coupling constant characteristic of the "iron" contribution to the susceptibility could be split into two contributions as well, of which the "d-band" contribution depends only on the electron concentration; the limiting values for high electron concentrations are proportional to the iron content of the alloy. Both separations indicate again that every Fe atom donates 3 electrons into the delocalized states of the alloy. The magnetic moment found here, however, is not in agreement with results derived from neutron diffraction experiments.