Kinetic Analysis by Chemical Relaxation Methods

The significance of chemical relaxation experiments (e.g., temperature jump measurements) for kinetic investigations of reaction systems involving any degree of complexity is examined. On the basis of a general solution of the relaxation problem, the properties of experimentally measurable relaxation curves—characterized by a relaxation spectrum—are discussed. Usually, actual theoretical or experimental determinations of complete relaxation spectra and their use for kinetic analyses are practicable only for fairly simple reaction systems. In the case of more complex systems an evaluation of relaxation experiments in terms of mean relaxation times is suggested. The mean reciprocal relaxation time is of particular significance. This quantity is shown to be fairly easily accessible experimentally. On the other hand, it can be computed without a complete solution of the relaxation problem. Examples are given to demonstrate the procedure and its potentialities with respect to the investigation of complicated reaction processes.