Abstract
THE glass stirring rod has largely been replaced by magnetic stirrers, shakers, ultrasonicators and other more sophisticated devices designed to produce homogeneous reaction mixtures in chemical systems. Most chemists carry out their reactions in the belief that any residual nonuniformities remaining in their reac- tion vessels have negligible effects on the results of their experiments. Evidence has been accumulating, however, that in at least some reactions with the kind of highly nonlinear kinetics that leads to several steady states or sustained oscilla- tion, significant concentration gradients arise despite the experimenters' best efforts to eliminate them. Menzinger and Dutt' now report quantitative measure- ments of macroscopic concentration gradients in the oscillatory chlorite-iodide reaction carried out in a stirred continuous- flow reactor. Concentration differences of up to 800 per cent are found between points near to and far from the stirrer shaft.