06/13/2007
Laser Alchemy?
Searching the Internet can be a weird and frustrating experience. Last week I was trying to find out how much I would have to pay if I wanted to buy some mercury, that silvery liquid element that in one form or another has become a major health issue. For example, due to mercury contamination, pregnant women concerned about their unborn children can no longer eat fish without considering the type of fish, its source and the portion size. But I digress. I consider myself pretty good at tracking things down on the Web. However, my quest to find the approximate price of mercury was truly frustrating. Every site I was led to by my search engine gave me either the cost of gold, the cost of various Mercury automobiles or the cost of downloading songs on the Mercury label!
Suddenly, I found myself on a site that gave me an answer. Last year, I could have bought a 76-pound flask of mercury for somewhat more than $700, roughly $9 -10/lb. Where did I find this answer? I should have known – the official online Web site of Senator and presidential candidate Barack Obama! I must confess that I don’t recall ever having visited the Web site of any political figure, let alone one of such prominence. And why did the words “mercury”, “cost” or “price” and perhaps another word or two I’ve forgotten, lead me to Barack?
Obama’s site posts a Chicago Tribune article dated November 27, 2006 that discusses a potential sale by the Department of Energy of some 1,300 tons of mercury. I hadn’t known that mercury was used in processing materials used to make hydrogen bombs and that alternate approaches had been found that don’t rely on mercury. The Tribune article states that the Defense Department also had about 4,400 tons of mercury on hand and had decided two years earlier not to sell it in order to avoid “human health and ecological risks.” The reason for the article being on Obama’s Web site is that it mentions a bill he had introduced in the Senate to ban American exports of mercury to other countries. His thinking was that the mercury could come back to haunt us in the form of some sort of pollution – sounds like a good argument to me.
Why was I interested in the price of mercury in the first place? I wasn’t really looking to buy any of the stuff. What spurred my search was an e-mail bulletin sent to members of the Materials Research Society (MRS). The bulletin contained a very brief 10- line report on a paper presented by University of Paris professor Francois Bozon-Verduraz and his group on May 31 at the MRS Spring Meeting in Strasbourg, France. In earlier times, what the professor reported would have created a sensation. The French workers claim to have changed mercury into gold; to transmute an element into gold was the alchemist’s dream hundreds of years ago. Today, transforming one element into another is not uncommon using nuclear reactors, cyclotrons or other particle accelerators. Hey, maybe this is the answer to our problem – convert all that mercury to gold!
What surprised me is that the French workers claim to have converted mercury into gold using a laser. They used a laser to irradiate a suspension of nanoparticles of mercury in heavy water, D2O (D is deuterium, a heavier isotope of hydrogen). (When I read the report, I couldn’t help thinking back to that ill- fated “cold fusion” and its association with heavy water.) The French group found that after about four hours of irradiating the colloidal suspension of mercury nanoparticles in D2O there was a significant quantity of gold formed. They propose that the laser light causes the mercury nanoparticles to emit X-rays. The X-rays are postulated to hit the deuterium and knock out a slow neutron from its nucleus. The neutron then gets picked up by the mercury, turning it into gold, according to the report.
Once again, I’m frustrated. If the nucleus of a mercury atom picks up a neutron, that just makes it a heavier form (isotope) of mercury. The short report on the French work didn’t say anything about the loss of a proton that is required to change mercury into gold. If a nucleus has 80 protons, it’s mercury – with 79 protons, it’s gold! Silly me – I hadn’t consulted Wikipedia. I also hadn’t noted that the MRS report mentioned that the mercury was enriched with an isotope of mercury, 196Hg (Hg is the chemical symbol for mercury). It’s apparently well known among the nuclear reactor crowd that if 196Hg picks up a slow neutron you form 197Hg, which is essentially what I just said. What I didn’t know is that 197Hg is unstable and decays into 197Au (that’s gold) through “electron capture”, an unfamiliar process to me. It seems that a negatively charged electron in orbit around the mercury nucleus gets sucked into the nucleus, converting a positively charged proton into a neutron, which has no charge. Loss of the proton leaves us with the 79 protons, i.e., gold.
Aside from my surprise that a laser could somehow transmute one element into another, the report also quoted Bozon-Verduraz as saying that he realizes that the process is not economically feasible because mercury is “so much more expensive than gold.” This surprised me as much as the science. I never considered mercury to be an expensive commodity. Hence my search on the Web for the price of mercury and the unexpected visit to Obama’s Web site.
The current price of gold is somewhere in the range of $600-700 an ounce, vastly more than mercury at around $10 a pound. So what’s up? Apparently, it’s that 196Hg. I checked my physics and chemistry handbooks and found that ordinary mercury contains a mere 0.15 percent of 196Hg. It must be the cost of that relatively rare isotope that makes the French group’s enriched mercury more expensive than gold.
With much less than one percent of those thousands of tons of mercury here in the U.S. being 196Hg, it looks like we’re stuck with it. One suggestion in the Tribune article on Obama’s Web site is that all that mercury could be stored in a climate controlled building the size of a Wal-Mart. I couldn’t help thinking that the “Wal-Mart” should be put in a huge bowl in case the container sprang a leak! Finally, even though our Editor, Brian Trumbore, promotes a conservative Republican philosophy, I must thank Senator Obama for relieving my search engine frustration.
Allen F. Bortrum
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