RSI PURIFIERS' RSD-Series of purifiers take advantage of the fact that only hydrogen and its isotopes (Deuterium, Tritium) can be made to pass through a palladium barrier. RSI utilizes palladium alloy tubing which has been optimized for this use.
Palladium-purified hydrogen represents the "state of the art" in gas purity. Analytical techniques have not yet advanced to the point where impurities can be detected in this product.
Hydrogen permeation through palladium is a metallurgical process in that hydrogen "alloys" with the barrier material, diffuses through it as protons and "de-alloys" from the far side of the barrier. The barrier remains absolutely leak tight to all other species than hydrogen and therefore serves as an absolute filter to pass only hydrogen (and its isotopes.)
Diatomic hydrogen, at an elevated pressure, is adsorbed (a) on a palladium-alloy barrier, where it disassociates into monatoms (b) which are absorbed into the barrier (c). Other species of gases are adsorbed, but do not dissolve into the barrier.
The monatomic hydrogen donates electrons to the electron cloud in the metal (d) becoming protons (H+), which diffuse (e) toward the far side of the barrier. At the far surface, the protons pick up electrons (f), becoming monatoms again, move to the outer surface (g), recombine to form diatoms (h) and break free as gaseous hydrogen (i).
All RSI purifiers work with a pressure differential from the inside of the tubing outwards, avoiding all possibility of collapse or crushing of permeation tubing and guaranteeing flow characteristics such that there are no stagnant areas which might concentrate impurities.