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1277was detrimental, while the powers of acacia and, particularly, of environment check one another, (c) the object of the work was t o gain a general idea of the behavior of commercial grades of certain substances under certain conditions as a guide t o possible further investigation from gelatin were enhanced by the presence of acid.Note-The points on the charts represent single determinations without a n y selection or rejection. Duplicates were not made because (a) adjacent points on a curve check one another, ( b ) curves differing in only one factor either a technical or scientific point of approach. Naturally, curves derived from highly purified substances might differ considerably from those here presented.

These authors excluded the dissociative mechanism from consideration because of their observation, which agrees with our results with methane, that the exchange reaction rate is so greatly reduced when heavy water is used in place of deuterium. In our case, where a dissociative adsorption of the methane seems unavoidable, we ascribe this slower rate in presence of heavy water to the lower accessibility of the methane to the surface owing to the known stronger adsorption of the water relative to hydrogen. Summary 1. The saturated hydrocarbon, methane, undergoes exchange with deuterium, methaue-d4 and deuterium oxide on active nickel catalysts at temperatures of 138°and higher.2. At 184°the rate of reaction of methane with methane-d4, deuterium and deuterium oxide decreases in the order given.3. The activation energies of reaction with methane-d4 and deuterium are ~19 and ~28 kcal., respectively.4. The mechanism of reaction is associated with an activated, dissociative adsorption of methane on areas of surface unoccupied by hydrogen-deuterium or deuterium oxide. Princeton, New Jersey