Induction times and exponential growth rates in branching-chain reactions

Abstract

The use of the partial-steady state hypothesis and the assumption that a branching-chain reaction can be characterized by the rate of reaction of a single intermediate are examined for a number of formal reaction mechanisms. Three kinetically-different mechanisms are distinguished, only one of which can be related to the reaction rate of a single intermediate. The use of the partial steady-state hypothesis also gives an incorrect result for one of the mechanisms. Relations between induction times, exponential growth rates, and reaction rate constants are derived and the interpretation of data obtained for the systems H₂+ O₂, H₂S + O₂, NH₃+ O₂, and CH₄+ O₂ is re-examined on the basis of these expressions. It is intended that the classification of reaction types will assist in interpreting information obtained on branching-chain reactions, particularly from shock-tube experiments.