Wandering Across Fields in Science

Irving R. Epstein

This is the story of how I wandered into the field of science that I’ve been studying for the past 45 years.  I was hired in 1971 by Brandeis University to teach physical chemistry and to do research in quantum mechanics – the subject of my doctoral dissertation and subsequent postdoctoral work.  My first couple of years, I taught freshman (as it was called then) chemistry and a graduate course in quantum chemistry.  I had some really fine students, particularly in the introductory course.  One spring, two of my best first-year (as they’re now called) students approached me and asked if it might be possible for them to do research with me over the summer.  I really liked the students and had funds to support them, but I couldn’t see how students who were just finishing their first year of college could do meaningful research in quantum mechanics, a highly mathematical and somewhat esoteric field.  So, I told them I’d look into it, and I took myself off to the library, which in those days still had loose journals on the shelves for browsing. 

Professor Irving Epstein of Brandeis University is seen in Waltham, Mass., Wednesday, March 22, 2006. (AP Photo/Robert E. Klein)

I picked up a few issues of The Journal of Chemical Education, which publishes articles not only about pedagogy but also about topics in chemistry that lend themselves to novel lecture demonstrations or laboratory experiments.  One issue contained an article about oscillating chemical reactions, a term I’d never encountered before.  The article described a fascinating phenomenon – you could dissolve a set of chemicals in water and the resulting solution would start off colorless, turn yellow after about five or ten minutes, go back to colorless in less than a minute, and then alternate between colorless and yellow at intervals of a few minutes for an hour or so before reverting to the colorless state.  I was intrigued, and a tiny bit skeptical, at the notion that a chemical reaction could behave this way. 

A little research revealed that I was not alone in my skepticism.  Chemists are taught to have a great deal of respect for the Second Law of Thermodynamics, which basically states that things run downhill (the entropy of the universe constantly increases, the Gibbs free energy of a reaction at constant temperature and pressure monotonically approaches a minimum…), and a reaction that went back and forth between a colorless state and a yellow one seemed to violate this principle.  It turned out that the first people to observe oscillating reactions had a terrible time getting their results published in peer-reviewed journals, even when they included data and recipes, precisely because reviewers insisted that what the authors had seen couldn’t possibly happen, since it violated the Second Law. 

The reviewers neglected the fact that the colored species whose concentrations were oscillating were neither the reactants nor the products of the reaction but rather intermediates present in relatively low concentrations.  The system could move in the direction predicted by the Second Law because the ups and downs caused by the oscillations of the intermediates were outweighed by the larger, one-way changes produced by the overall reaction that converted reactants to products in much larger quantities.  They might also have stopped to consider that living organisms are full of oscillating chemical reactions, as illustrated by the 24-hour cycles of hormonal and other concentrations in the body.

Since, as a theorist, I had no lab of my own, I asked a colleague, Ken Kustin, an inorganic chemist, if I could try the reaction in his lab.  He readily agreed, and we collected the needed chemicals from the stockroom, mixed them up, and voila!  The reaction mixture oscillated in color exactly as described in the paper.  Captivated by this display, we agreed that these reactions would make the perfect topic for an undergraduate research project, and Ken offered me a corner of his lab for the students to work in that summer.  To get them started, I asked the students to read and reproduce the observations in the classic paper devoted to characterizing the best-known oscillating reaction, the Belousov-Zhabotinsky (BZ) reaction.  At the time, there were only three such reactions.  Two, including the BZ, had been discovered accidentally, and the third was a hybrid of the first two. 

After a few weeks, one of the students came to me and told me that he had been able to reproduce all of the work in the classic paper with one exception. The paper stated that trace amounts of chloride ion totally suppressed the oscillation, but he had (accidentally!) dropped a significant quantity of chloride into an oscillating mixture, and, after a brief hiatus, the oscillations had resumed.  Reluctant to accept the result of an undergraduate’s accident over the published wisdom of senior investigators, I told him to redo the experiment under controlled conditions.  He did so, and returned to tell me that he had obtained the same outcome.  Then I asked him to perform the experiment yet again, with me looking over his shoulder at every step.  Same result! 

We spent the rest of the summer figuring out what was going on.  It turned out that the earlier investigators had noted that when they used an electrode that continuously leaked a tiny amount of chloride into the BZ mixture the oscillations ceased, so they concluded that a trace of chloride permanently killed the oscillatory behavior.  In our experiment, we added more chloride initially, but in one shot.  This allowed species in the reaction mixture to consume the chloride, and when it was gone, the oscillations were able to resume.  We worked out a detailed mechanism for the process, wrote it up and published it in the Journal of the American Chemical Society, the most prestigious journal in chemistry.

Buoyed by this success, the following summer, I invited another outstanding undergraduate to study the BZ reaction with me.  I suggested that he look at the effects of adding iodide, rather than chloride, to the system.  Since iodide is a halide, in the same column of the Periodic Table as chloride, I expected it to have very similar effects.  To my surprise, he found that at some concentrations, iodide behaved as anticipated and inhibited the oscillations, while in another range of concentrations it appeared to induce oscillations.  Again, we were able to decipher the mechanism of this unexpected phenomenon and publish our analysis in JACS.

At this point, I was getting hooked on oscillating reactions.  Like many chemists, I had initially been attracted to chemistry by playing around with mixing chemicals and seeing them turn color.  In quantum mechanics, nothing ever turned color.  You did your calculations, input your parameters to the computer, and pored over the resulting output.  Here, things not only turned color, they did so repeatedly and unexpectedly.  As I got more into the field, it occurred to me that studying a phenomenon whose only examples resulted from serendipity was not an intellectually satisfying situation.  If you really understood oscillating reactions, you should be able to build one.  Ken Kustin and I talked about this a lot, and we eventually came up with an idea for how to construct chemical oscillators.  It would require some funding, so we wrote a proposal to the National Science Foundation, sketching out how we would do it.  The proposal was rejected, not once or twice, but three times.  Typically, some of the reviews would say this was a great idea that ought to be funded, while others would call it an interesting idea that was unlikely to work.  We decided to give it one last try, and by some good fortune, we accumulated enough positive reviews that the proposal was funded.

We were able to hire two outstanding collaborators, Patrick De Kepper from France and Miklós Orbán from Hungary, and within a few months of their arrival, we had succeeded in generating the first deliberately designed oscillating reaction.  Over the next several years, our technique yielded more than a dozen new chemical oscillators, and we began to explore more complex problems – how oscillators behave when they’re coupled together, how to describe oscillating reactions at a molecular level, what kinds of spatial patterns these reactions can produce, etc.  I abandoned my research in quantum mechanics and have devoted my attention to oscillating reactions and related phenomena, such as pattern formation and chaos, ever since.

As a final note, which attests to the narrow focus to which scientists may be subject, I recall that a few years after my transition out of quantum mechanics, and in particular the area of Compton profiles, in which I had done some important work, there was a timid knock on my office door.  “Come in,” I shouted.  The door slowly opened, and a gentleman in a tweed jacket timidly poked his head in.  “P-p-professor Epstein?” he stammered.  “Yes,” I replied.  He rushed in and embraced me.  “I’m so glad to see you,” he blurted, “I thought you were dead.”  “Why would you have thought that?” I asked.  (I was all of about 35 at the time.)  “Because you suddenly stopped publishing on Compton profiles and haven’t been heard from in years.”  I informed the gentleman, whose name I now recognized as a rare devotee of Compton profiles, that I had indeed moved on, but not in the sense he had feared.  Remarkably, for someone who thinks of himself as having a short attention span, I have managed to focus my research efforts for over four decades now on a single, very rich, area of inquiry and have thus avoided further encounters of the kind I’ve just described.

Additional Reading:

A global salute to Irving Epstein, a ‘founding father of chaos’