Uses of the transit time distribution in kinetic flow systems

We investigate the distribution of transit or residence times of a trace reactant in laminar flow. We present measurements of this distribution for hydrogen atoms in a typical flow system, and show that the results are consistent with known theory and previous measurements of the diffusion coefficient. The use of the measured distribution as a diagnostic of flow behavior is discussed. It is also shown that the measured or calculated transit time distribution can provide a convenient means of correcting results of kinetic measurements for the departure from plug flow. In the case of firstorder, and also second‐order decay of a single reactant, this correction is a useful approximation to the more rigorous solution of the partial differential equation for diffusion and reaction in laminar flow. Effects of the deviation from plug flow on a complex rection system are illustrated qualitatively for the H + NO 2 titration system.