[gilleain]

To save people looking it up, _aqua regia_ (wikipedia- 'literally "regal water" or "royal water"') is a mixture of nitric acid (HNO3) and hydrochloric acid (HCl) in a 1:3 ratio.

It was used by alchemists, as it can dissolve gold.

[jgamman]

niels bohr dissolved the nobel prize medals of colleagues in it and left it on his office shelf during wwII - the committee recast them after the war https://www.aip.org/history-programs/news/invisible-prize