The techniques of hydrogen diffusion through a permeable diffusion septum are well known to the art, and the distinction between such processes and passage of gases through porous film or membrane need not be further explained in detail. Suflice it to say, that the process of permeation utilized in the present invention involves the passage of hydrogen gas from the high-pressure side of a non-porous septum through the solid material of the septum and out the low-pressure side thereof. The permeable septum which is employed in the practice of the invention is necessarily non-porous, that is essentially free from holes, voids, pores or other defects which affect the continuity of the film.