Investigations of the palladium/hydrogen system about the critical point of demixing revealed surprising results in thermodynamic behaviour – i.e. ordering of the dissolved hydrogen – and in electronic effects, i.e. magnetic susceptibilities: Although the equilibrium hydrogen pressure increases with temperature smoothly and without irregularity from the two‐phase region through the critical point into the homogeneous supercritical phase – at constant (critical) concentration – the lnp – 1/T line exhibits a sharp curvature (“kink”) at the critical point.—The occurrence of the kink is shown to be a consequence of the unsymmetrical shape of the coexistence curve. This shape is related to a decrease in entropy that grows on quickly with rise of hydrogen concentration (third power), indicating a strong ordering tendency even in the supercritical phase. The Bragg‐Williams approximation, mostly applied in connection with mean‐field theory, is therefore not adequate, actually, to this system.—The supercritical phase enables investigation of electronic properties along broad ranges of continuously varying concentrations. Measurements of the magnetic susceptibility of PdH_n in this range with 0 < n < 0.55 in comparison with Pd_1‐xAg_x alloys revealed higher values for PdH_n at equal valence electron concentration (n = x). In this aspect the rigid‐band model, obviously, does not correlate the two systems.