Diffusion of Gases through Platinum

Hydrogen diffuses through heated platinum, but less rapidly than Graham's experiments would suggest. Methane, despite its low density, does not diffuse through heated platinum, neither do oxygen, nitrogen, argon, and helium. The diffusion of hydrogen through platinum has been studied by many investigators, notably by Winkelmann, who shows that its rate increases after the platinum has been heated for some time, in consequence of the crystalline structure assumed by the metal. The diffusion of hydrogen through platinum at red heat is not directly proportional to the pressure of the gas. Probably this is due to the diffusion being accompanied by dissociation of the hydrogen molecules, the atoms, only, of the hydrogen passing through the metal.