“…20, 206 (1932 * See also the following references which were either overlooked or were published after this paper was written: peared papers by Eyring, 19 Eyring and Sherman, 20 Urey and Rittenburg, 21 and Polanyi. 22 Other methods of concentration have been tried by Newell and Ficklen, 23 Washburn and Smith, 24 Taylor, Gould and Bleakney, 25 Lewis and Cornish, 18 and Cremer and Polanyi. 26 Bradley and Urey 27 have studied the concentrations in natural hydrogen from several different sources.…”