Gold
A metallic element with atomic number 79; soft, highly malleable, and almost unreactive with air and water, which made it a long-standing material for currency and jewelry.
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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