Professor Varma handed me a manuscript with the subject title over 3 decades ago. Mathematical models for ideal reactors and for diffusion and reaction in porous catalysts had been developed. Reaction engineers in academia were determining uniqueness, multiplicity, and stability criteria for model reactions. Meanwhile, practitioners were characterizing complex feeds and developing models for simulation and control of industrial reactors.

Stirred pots and tubes are still used to enact chemical and biochemical transformations. The present talk will present several examples from the author's experience.