Friday, March 9, 2007

Paying Attention

Chlorine gas is quite the little charmer, from a photochemist’s point of view.

Most gases need ultraviolet light to get frisky, but not chlorine. No, Cl2 absorbs into the mid-range of the visible (somewhere around yellow, as I recall), and does so pretty emphatically, photolyzing at several percent per minute in full sunlight. When it absorbs light, it decomposes into two chlorine atoms, radical atomic chlorine, which is mega-reactive, yanking hydrogen atoms off of even methane at a pretty fast rate. For larger hydrocarbons, the rate is “collisional” which means that when the Cl atom hits, the probability of reaction is 1.

So Whitten and I got interested in chlorine because it can goose the smog process, and it was probably doing so in Henderson, Nevada, and we had a small contract to assess the situation. Henderson had been having smog episodes on cold December mornings, when the thermal inversion was very low (trapping the pollution very near the ground). Usually smog does not go so well in the cold, but in Henderson, apparently, the chlorine trumped the cold. The chlorine came from a company called Timex, which made titanium, not watches, with a process plant that was new in WWII, and leaked like a sieve.

As part of the work, I did a literature study on chlorine photochemistry, which was interesting. The “smog accelerator” effect from chlorine had been used since the mid-sixties as a way to enhance radical initiation in smog chamber experiments, and after that, the phenomenon of ozone destruction in the stratosphere had led to a fair number of papers.

But before the 1960s, there wasn’t very much about chlorine photochemistry in the literature—until I got back to the 1920s and 1930s. Beginning around 1920, there was a sudden boom in the study of chlorine in the gas phase. That boom lasted until the mid- to late 1930s and then trailed off. By the time of WWII, it was a moribund field.

It takes no great insight to realize what caused the sudden interest. The Great War had left a wake of disabled veterans who had been victims of gas attacks, chlorine, phosgene, and bis-(2-chloroethyl) sulfide (“mustard gas”). I also got interested in phosgene chemistry a while after our Henderson study (phosgene also contains chlorine, and it’s a decomposition product of chlorinated hydrocarbons like methyl chloroform), and all the information I could find on it also came from this time period.

This is, of course, a very ordinary description of the ordinary behavior of science, or, indeed the ordinary behavior of human beings. We study things that interest us; we pay attention to our interests.

Some of the more extreme advocates of relativism and deconstruction claim that science is an enterprise no different from any other, and that the results of science are conditioned/determined/biased/required by the social, cultural, or gender outlook of the scientific community. One can, of course, deconstruct such claims by noting that they are made by one class of university academics who are locked in the usual struggle with a different class of university academics, but that is a petty, or at least trivial insight.

Scientists generally hold themselves to be “reality based,” to use another culturally biased phrase and I strongly agree that no amount of cultural relativism will make N-rays exist and X-rays imaginary. But that is not the be-all and end-all of bias and cultural determinism. No, the phrase “where one’s interests lie” says a lot about science. We study chlorine in the 1920s and 1930s, not because of some rational, objective criterion of how chemistry should progress, but because cultural factors made it important to do so. I can point to a number of objective truths that my colleagues and I uncovered over the course of my career in science, but it would be folly to think that we were not looking “where the light’s better,” under the streetlights of funding, social interests, and group status within our little part of the scientific community.

If I had to make my own philosophical stand, holding up my own interpretation of both free will and the forces that work against it, I’d give that as a capsule summary: it has to do with paying attention, to what, and for what reasons.

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