Contribution to the study of a method for measuring continuously the isotopic effect. The search for an isotopic effect during the reduction of cuprous oxide by a 12CO - 14CO mixture (1962)

The determination of an isotopic effect between the two reactions: 12CO + Cu2O → 12CO2 + 2 Cu 'light' reaction 14CO + Cu2O → 14CO2 + 2 Cu 'heavy' reaction is possible if the respective kinetics are known. The condensation, during the reaction, of the carbon dioxide formed, and the measurement as a function of time of the residual carbon monoxide pressure, makes it possible to deduce, uninterruptedly, the 'light' reaction kinetics. The 'heavy' reaction kinetics are obtained by measuring continuously, in situ, the radioactivity of the residual reactant gas as a function of the time. The apparatus used for this is a plastic scintillator counter. A calibration curve of the measured radioactivity as a function of the reactant gas pressure in the absence of reaction makes it possible to compare the kinetics of the 'light' and 'heavy' reactions. The reaction temperature is chosen such that the reaction rate is sufficiently slow, so that the variation of the radioactivity during unit counting time is negligible. (author)