I'm a writer. I have a scenario in which a sizable amount of gold needs to be rendered unusable, preferably completely destroyed. I know an acid like aqua regia is able to dissolve gold, but would there be a way to make it impossible (or at least not worth the cost) to chemically salvage the gold from the acid, or another way to permanently destroy gold?
Other than a nuclear reactor, the only other chance is to dump it into a volcano. Having a much higher density than magma, it will just fall through until it hits earth's mantle. Then it's really gone. OK, dissolved and diluted in the Atlantic is also quite safe.
P.S. Warning: If the bullion gets stuck in the volcano, which later explodes Krakatau-style, your gold brick might land in someone's front lawn. Making a hole five meters deep, but it may be salvaged easily.
As other answers have pointed out, you can't 'destroy' gold chemically.
Putting it in a nuclear reactor for an extended period of time will functionally convert most of it to an isotope of mercury. If you really want to get rid of it, and you have lots of funding, you could launch it on a rocket into the sun (or another star, or better yet a black hole).
If you just want it to be very difficult to recover, you have lots of other options depending on the desired difficulty:
Dissolving it in aqua regia is a decent start, as you can then dump the result into almost any large body of water, which would make it extremely difficult to recover.
Dropping it into an active but not erupting volcano would be decent too, it will melt reasonably quickly (gold has a somewhat low melting point), and then diffuse throughout the magma.
Somewhat lower tech, but if the setting is before submarines became common, drop it in the ocean over a subduction zone. It will sink very quickly, and slowly be pulled into the mantle by the subduction zone, so if you drop it close enough, it will end up being unrecoverable by the time people can go that deep.
This won't really get rid of it, but gold dissolves readily in mercury at room temperature to form an amalgam. The resulting amalgum can actually be pretty easily separated by just letting the mercury evaporate, but it is a pretty neat way to get rid of the gold temporarily.
Not destroying gold, but still giving a good appearance, is this time-honored story of how two golden Nobel prizes were "hidden" from the Nazis by dissolving the gold into aqua regia. The aqua regia, of couse, had only a limited shelf life; but the soluble gold species it produced could be retained indefinitely. After the war the gold was reduced, recovered, and recast into the Nobel prizes.
If you don't use any nuclear technology, you can't destroy gold.
Everything that you can do to the gold, can be undone.1
What you can do: you can make its reconstruction economically infeasible.
However, gold is
- Very stable (chemically) and non-reactive.
Because of these, gold can be easily extracted from practically any gold compound.
What could work: Maybe mixing it into high-reactive nuclear waste, for example into freshly depleted nuclear fuel rods, and then turning off their cooling. (Depleted fuel cells should be cooled for a while after they are removed from the reactor, to avoid them melting because their own radiation.) The result will be that they melt, and the resulting corium will mix with the gold therein.
1 As @IvanNeretin mentioned in a comment: dissolving the gold in an acid, and then pouring this into the ocean (or throwing in the toilet) would work.
Gold is extremely difficult to get rid of, either chemically or physically.
Gold is produced when a massive star goes supernova. Every single atom of gold in the entire universe is the result of the death of a star. So, a lot of energy went into the actual creation of the gold to begin with. More energy will be needed to destroy it's very atomic structure.
Ways to get rid ot it:
- Grind it to dust and disperse it;
- Dissolve it in aqua regia (as mentioned in various other answers);
- Melt it in a kiln and mix it with something else (metals or ceramics);
- Others suggested to dump it in a volcano or something like that to make it disappear into the planet's interior
- Reacting it to a halogen to make AuCl3, AuBr3 or AuI. Any aurohalide can of course be reduced back to it's constituent parts.
Gold has one principal isotope (gold-197) and all other isotopes are unstable and decay mostly by beta emission into isotopes of mercury. Given that its cross section is 98.7, it will act as a neutron poison in reactors transmuting with a 2.7 day half life into mercury-198, which is stable. Given the cross section and short half life, gold was considered a salting agent in radiological weapons. It has been reported that the plutonium pits of US nuclear weapons are all gold-plated to prevent corrosion with the air. The only way to get lighter isotopes would be through spallation.
As you know you cannot destroy an element. Aqua regia could dissolve it but not destroy it. As a matter of fact, George de Hevesy dissolved Max von Laue and James Franck's gold Nobel Prizes medals in aqua regia during the Nazi occupation of Holland. The stupid Nazis were oblivious to the solution sitting in a flask on a shelf at the Niels Bohr Institute. After the war, de Hevesy precipitated the gold and the Nobel society minted them new medals from the comingled gold of their original medals.
In William Gibson's novel Spook Country, a large quantity of cash is exposed to a radioactive source making it radioactive and permanently unusable. The same thing could be done to "ruin" gold, by contaminating it with a radioactive substance.
Use something that can shot waves of protons with great dynamic to make protons and neutrons separate in gold atoms so it not gonna be gold again! (but if you can decomposite it so you can reform it in some way)
( Just like you use your hand's force to cut a cheese off)
Like an explosion of a neutron star.
Or in an imaginary scenario when you use a rocket to carry all the gold amount and let it detonate itself with a nuclear bomb so there will only be gold dust in the vacuum.
I remember reading many years ago that you could transmute mercury into gold by a suitable nuclear reaction, but it was actually cheaper to transmute gold into a very pure mercury isotope using a different nuclear reaction.