October's Element of the Month: Rhodium!

October's Element of the Month:

Rhodium!
Rh
45

Atomic Mass: 102.90550 amu
Melting Point: 1964 °C
Boiling Point: 3695 °C

Rhodium is the wallflower of the precious metals. Gaudy Gold gets heaps of attention, of course, and Silver and Platinum are Very Big Deals, and although Palladium isn't exactly playing in the same league, the minerally inclined among us would recognize it as part of the set. But despite that it is rare, shiny, chemically stable, and would probably make a perfectly jolly coin, Rhodium gets very little love indeed.

"How precious is precious?" you ask. Well, about as precious as Gold, at least last weekend, at least according to one dodgy-looking internet commodities reporting site.

That's pretty precious. "Precious as gold" is downright proverbial. Like a lot of commodities, though, the price of Rhodium has been wildly volatile for the last decade or two, as the demand for various kinds of stuff among the world's humans has spiked just as we were running out of the easily available supply. I'm sure it's nothing to be concerned about.

Truth is, we could get by fine without Rhodium if we had to. Its major human uses are only as a catalyst in catalytic converters and as a corrosion-proof coating for other metals, and there are other Elements that can handle that kind of job. It doesn't do anything biologically, if you were worried about that.

The Centerfold!

The silver-grey sheen of pure Rhodium.

If we got desperate, it would be possible to stack up some atomic waste and wait for Rhodium to appear spontaneously through the decay of Uranium and other radioactive elements. The lure of free precious metals has provoked a lot of extreme behavior in the past, but since this particular method would involve tending an almost unbelievably dangerous inventory of material for a century or two, nobody seems to be giving it much of a go quite yet.

Rhodium was identified by brainy English guy William Hyde Wollaston in 1803. He discovered Palladium, too. His Elements work was not entirely altruistic; what he was really after was the purification of Platinum. For a couple of decades, he was the only person who knew how to produce really pure Platinum, and he used his monopoly to create quite a pile. Meanwhile, he also made important discoveries in optics and electromechanics. Why can't you be more like William Hyde Wollaston? Well, he wasn't perfect: he incorrectly convinced people that Tantalum was the same thing as Niobium, and he was on the royal commissions that stuck the English speaking world with the imperial system of measurement, back when it could have gone metric pretty painlessly.

Incidentaly, Rhodium isn't named after Cecil Rhodes like you'd think. It's named from the Greek "rhodon," or pink, because of the rosy little crystals of sodium rhodium chloride in which it first revealed itself to Mr. Wollaston.