Two plateaux are observed in both the absorption and desorption isotherms of palladium hydride. For the absorption isotherm, a change in plateau pressure is observed at a hydrogen-to-metal (H/M) ratio of about 0.35 for all temperatures studied. For the desorption isotherm, the change in plateau pressure appears to be a function of temperature, ranging from an H/M ratio of 0.18 at 80° C to 0.3 at 140° C. These data are interpreted as being experimentally observed boundaries to an equilibrium phase line located in the miscibility gap of the palladium/hydrogen phase diagram. This new phase does not appear to be a stoichiometric compound, but rather its composition seems to vary with temperature.