“…It has two consequences: First, the order of hydrogenation with respect to ethylene should not be equal to zero, contrary to svhich has been found by numerous authors [11]. In our case we really found it to be 1 [12]. Second, if we succeed in decreasing the catalyst activity for hydrogenation, in other words, if we can achieve a constant ethylene concentration on the surface the radioactive ethylene should appear, at least in small amounts, in the gas phase.…”