The Hydrogen Diffusion Rate Discontinuities of Palladium

The structure of sensitive properties of palladium metal are found to change discontinuously in such a way that the hydrogen concentration and the rate or hydrogen diffusion alter suddenly at a reproducible geometric series or hydrogen pressures. The data of two low pressure concentration studies and a number of low pressure diffusion rate studies are tabulated and plotted so as to show the discontinuities. The best set of values for the critical pressure, obtained by plotting a curve of "breaks", is: 2.6, 5,3, 10.6, 21.3, 42.5, 85, 170, 340, and 620 microns of mercury. A collection or absorption and diffusion rate data from the literature suggests an extension of this series to complete hydrogen saturation (Pd4 H2) at 350 millimeters of mercury. A tentative statistical theory is proposed of the penetration or ionised atoms Into a crystal which has an intrinsic secondary structure. The theory predicts the concentration isotherm in terms of the transmission discontinuities. It describes a secondary structure which has finer spacing tor each successive higher concentration step and enables a calculation or the value of each spacing. Several microphotographs or the palladium surface are shown. Measurements of the photographs are compared with the spacings predicted by the theory.