Aqua regia
Appearance
Aqua regia (latin for "royal water") is a mixture of concentrated nitric acid and concentrated hydrochloric acid. It is one of the few reagents able to dissolve gold and platinum.
It is also known because painters usually clean in it their brushes after use.
When the Nazis invaded Denmark, the Hungarian chemist George de Hevesy dissolved the gold Nobel Prizes of Max von Laue and James Franck into aqua regia and placed this reagent on a shelf in his laboratory at the Niels Bohr Institute. After the war, he returned to find the solution undisturbed and precipitated the gold out of the acid.
Cites for the Nobel Medal story: