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E:change hCtCrog&ne sur tungsthe du cli10rc~~ radioactif en tre I'acide chlor-hydrique et le chlorure de mCthyle par R. COEKELBERGS, A. FRENNET(*) et P. A. GOSSELAIN(**) SUMMARYThe isotope exchange reaction of C136 between KCl and CH,CI has been investigated a t 262,2OC on evaporated tungsten surfaces. Rates have been measured over a pressure range from 4 mm t o 300 mm and were found to be proportional to the first power of the CH,CI pressure and to pass through a maximum with respect to HCI. Data can be explained with a Hinshelwood-Langmuir mechanism.However, it has been observed by mass spectrometry that CH, was evolved on the catalyst when heater1 with CH,CI; the heating with CH,CI-HCI mixture or HCI alone produces H, only. It has been further shown that a pretreatment with CH,Cl lowered the rate. These facts strongly suggest the initial formation of W-Cl centers, entering in an exchange reaction with CEI,CI and IICl physically adsorbed. A mechanism can be developed in terms of these renters which also agrees with experimental results, and is more satisfactory than the Hinshelwood-Langmuir mechanism.

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