The Induction Period in Chain Reactions

The conditions for the establishment of a stationary state in a system of consecutive reactions can be investigated quantitatively in a sufficient number of cases to permit precise criteria to be formulated generally for the length of the induction period (i.e., prestationary state period) in chain reactions. These are given as functions of the individual rate constants for the separate reactions, the extent of the reaction and the percent of stationary state concentrations achieved. Such relations provide a means for the evaluation of the self-consistency of experimental data with proposed mechanisms and also provide numerical limits on the values of individual rate constants.

Various chain reactions are examined in the light of these criteria. Of the hydrogen-halogen reactions, the H2–Cl2 reaction mechanism does not fulfill the stationary state requirements, and it is probable that many of the discordant results found in this reaction arise from this difficulty.