Aqua regia
A strongly oxidizing mixture of concentrated hydrochloric and nitric acids, usually in a 3:1 volume ratio. It can dissolve noble metals such as gold and platinum that resist either acid alone.
When Nazi Germany occupied Denmark in 1940, chemist George de Hevesy dissolved two colleagues' Nobel Prize gold medals in aqua regia and left the yellow liquid on a shelf. The Nazis never noticed it. After the war, Hevesy recovered the gold and the Academy recast the medals.
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