Parahydrogen Conversion on Tungsten

Abstract

THIS reaction¹ has been reinvestigated using a reaction tube containing a second short filament adjacent to the catalyst filament, so that adsorbed films on the latter might be detected by a measurement of their contact potential². In this way it was shown that the filament in its most catalytically active state was free from adsorbed oxygen. Under these conditions, as J. K. Roberts³ has pointed out, the clean wire on exposure to gaseous H₂ takes up a stable film of hydrogen, which does not evaporate appreciably at room temperature, and so cannot give a para H₂ conversion by the mechanism suggested by Farkas¹, namely by H₂+2W ⇄ 2WH (where W indicates a surface atom of tungsten). It is, however, possible⁴ that the conversion might occur by a surface interchange reaction of the type pH₂ + WH → ₀H₂+ HW, and this mechanism gains support from the following experiment.