Kinetics of the Isotopic Competitive Method

We shall consider, first, the kinetics of a system undergoing an isotopic competitive intermolecular reaction, first order in the concentration of the isotopic species and of arbitrary order with respect to other reactants. Later we shall show that the results are applicable to intermolecular isotopic studies of any higher order 

From our assumption of reactions first order in A or A, it follows 

Simultaneous solution of this set of differential equations with the boundary condition A = A when A = A0 yields 

Where Raf — (A/A ) after the fraction / of the substrate of chemical species A has reacted, and is the initial ratio (A/A )0. Since the fraction reacted, /, is given by the stoichiometric relationship 

The method then consists of the determination of the isotopic ratios of the original substrate and Raf after a stoichiometrically 

A similar but more detailed analysis of the effects of errors in the determination of kjk by specific activity measurements of the 

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