Alchemy?

[TheBigDog]

My wife is taking a prep course for nursing school. She had a questing this week on her assignment asking if you could make gold from mercury. I told her no (as asking me is what amounts to research in this house). Her teacher told her that the answer was wrong. So we looked it up on the net and found that this can apparently be done in a linear accelerator, but it would take 1,000,000,000,000,000,000,000,000 years to get a penny's worth of actual gold. Since that number is longer by a huge margin that the age of the universe itself, would the answer 'no' be correct?

Bill

[CraigD]

Originally Posted by TheBigDog

My wife is taking a prep course for nursing school. She had a questing this week on her assignment asking if you could make gold from mercury. I told her no (as asking me is what amounts to research in this house). Her teacher told her that the answer was wrong. So we looked it up on the net and found that this can apparently be done in a linear accelerator, but it would take 1,000,000,000,000,000,000,000,000 years to get a penny's worth of actual gold. Since that number is longer by a huge margin that the age of the universe itself, would the answer 'no' be correct?

Bill

I believe the 10^24 years figure is badly overstated. By various accounts, several kg of gold has been transmuted from lead by knocking 3 protons (atomic # 82-3 = 79) from each nucleus (and 12 or so neutrons), mostly due to accidental collisions with lead shielding in linear and cyclotron accelerators. Intentional transmutation of lead to gold wasn’t reported until Glen Seaborg did it to a few thousand atoms in 1980 – well less than a penny’s worth.

Mercury is next to Gold in the periodic table – atomic # 80 vs 79 – so should be easier to transmute into Gold than Lead. Since mercury is less commonly used around accelerators than lead, it’s possible that its transmutation to gold has never been observed, intentional or otherwise – although a 1946 American Physical Society paper (http://link.aps.org/abstract/PR/v70/p910) describes the opposite transmutation – gold to mercury, specifically the difficult-to-isolate isotope Hg-198 – of a fraction of 1 oz of gold.

Transmuting anything into useful, precious gold is a tricky, hit or miss process. Not only must you dislodge exactly 1 proton, you need to end up with either exactly 118 neutrons, or you get radioactive gold that decays into either platinum or mercury with a half-life of 3 to 186 days, reducing the yield, and increasing the cost, even more.

It’s not so much that nobody is capable of making gold from mercury, as that no one’s much interested in doing it more than needed to verify that it can be done – a few thousand atoms totaling perhaps 10^-24 kg. Accelerating protons to energies (speed) high enough to dislodge a proton from an atom of mercury is expensive, both in terms of the cost to build the accelerator, and the cost of energy to operate it (accelerators are amazing energy pigs, equivalent on average to small cities), so even producing kg of gold would be a money-losing process. Then there’s the problem of getting the science directors in charge of an accelerator to waste time doing on a bulk manufacturing process that doesn’t add any new scientific knowledge. In short, unless it happens accidently, or in some purposeful way that doesn’t interfere with the accelerator’s regular research schedule, it ain’t gonna happen.

One area in which it may be economically practical to use accelerators to transmute elements is in the disposal of certain very dangerous nuclear fission by-products (isotopes of plutonium, neptunium, americium, etc.). Some have suggested that, rather than costly waste disposal facilities to lock these away essentially forever (with uncertain reliability – “forever” is a hard service life to design for!), they cold be transmuted into useful or least quicker-decaying isotopes.

This reminds me of our Star Trek “replicator” sub thread in the “moneyless society” thread. These fictional devices would presumably be able to turn mercury into gold by the bucketful, but consume the energy equivalent of earth-years of generated electicity, and require wildly science-fictional subatomic imaging technology, to do so. Making cups of tea would presumably have similar energy costs. The only thing that can make such technology practical, assuming the imaging problems are solved, is energy orders of magnitude cheaper than it is now – in effect, a civilization approachin type 2 on the Kardashev scale. This is not likely to happen anytime soon

[TheBigDog]

Thanks Craig! So much for my plans for building a linear accelerator in the basement and forging gold from thermometers. Back to the drawing board...

Bill