MERCURY

RUDY M. BAUM , C&EN WASHINGTON

It is among the most seductive of elements. Quicksilver. The only metal that is liquid at room temperature. Indeed, mercury's chemical symbol, Hg, derives from the Latin name for the element, hydrargyrum--literally, liquid silver.

Mercury is one of the handful of elements that have been known since antiquity. Alchemists were beguiled by it, convinced that it held the key to transmuting base metals into gold.

And like so many seductive things, mercury is dangerous. The ancients also knew that mercury was highly toxic. Compounds of mercury have been used in medicine and as disinfectants for centuries. Calomel--Hg₂Cl₂--was long the only treatment for syphilis, although the treatment was nearly as awful as the disease.

	DROPPING IN Droplets of mercury on a green surface. The surface tension of mercury is so high that the smaller droplets form almost perfect spheres.
	PHOTODISC

That knowledge didn't stop me and a few of my scientifically oriented friends, of course. The attraction of quicksilver was far too great.

"You can put a penny in it and it will coat it like that!" one said. "Can't get it off, either."

So in went the penny, and sure enough, out it came shining like a newly minted dime. But more than that, the penny had that unmistakable slipperiness you associate with mercury. And you couldn't rub it off. What had happened? Did the mercury react somehow with the copper of the penny? We didn't know where to turn, and we certainly weren't going to ask our science teacher, because we knew we weren't supposed to be performing this particular experiment.

We wanted to do something with the mercury. We thought we might be able to make a barometer, but the problems associated with filling a glass tube with mercury and somehow sealing one end of it were beyond us technically. We proved it was conductive with a battery, wire, and light bulb. We ran it through plastic tubing, fascinated by the lightning-quick flow of the metal. Although we were reasonably careful, we probably contaminated the classroom with more mercury than some government agency deems acceptable.

I mentioned the mercury to my father over dinner, and he recalled his service in Europe in World War II. He and his brother Walt were both in the infantry, and they met twice while they were crossing Europe and serving in the occupation forces after the war ended. On one of those occasions, Dad met his brother at a small railroad freight yard in Germany. Walt was among a contingent of Army engineers accompanying a freight train transporting a shipment of mercury. Dad recalled Walt opening up the doors of one of the boxcars to show him a single layer of flasks of mercury spaced evenly across the floor of the railcar. They were so heavy they couldn't be packed any more densely. Dad didn't remember where the train was coming from or where it was going, but he did remember that it carried that load of mercury.

I can't say that my early exposure to mercury affected my much later decision to become a chemist. Those seventh-grade experiences were soon a distant memory. Mercury isn't a particularly interesting element chemically, and it's so poisonous that it doesn't play a role in chemistry sets, even those of my boyhood. (I went to college expecting to major in biology; my shift to chemistry had much more to do with the Duke University chemistry faculty than my early experiences with a chemistry set.)

But I've always retained a mild fascination with mercury. I still find it unfortunate that mercury has been banished from thermometers for safety reasons. A mercury thermometer has more gravitas than one filled with a red liquid. And a frisson of fear, as well: I remember clearly C&EN reporting in 1997 the death of Dartmouth University chemistry professor Karen E. Wetterhahn after she was exposed to methyl mercury while preparing a nuclear magnetic resonance standard.

When C&EN Editor-in-chief Madeleine Jacobs mentioned more than a year ago that we should celebrate C&EN's 80th anniversary in 2003 and asked whether I had any ideas for a special issue of the magazine, my eyes went to the periodic table hanging on my office wall. What's element 80? Why, it's my old friend mercury. Other anniversaries are designated silver, gold, and diamond, I thought, so why not call this our "mercurial" anniversary? It was a silly idea, but it started the discussions that led to this special issue of C&EN. We hope you enjoy reading it.

Rudy M. Baum is C&EN's deputy editor-in-chief. He has covered a variety of topics in chemistry, the interface of chemistry and biology, and science and society for the magazine for more than 20 years.

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