The Mechanism
In the 1930s two German physicists had smuggled their gold Nobel medals out of Nazi Germany to Niels Bohr's Institute in Copenhagen for safekeeping — exporting gold out of the Reich was a serious crime, and the engraved medals could be traced straight back to them. When Germany occupied Denmark in April 1940, a chemist working at the institute realized the medals had to vanish before the building was searched. Burying them felt too risky, so he reached for chemistry: he dissolved the gold in *aqua regia*, a corrosive mix of nitric and hydrochloric acid — one of the few things that eats gold. It is a slow reaction; he had to wait through anxious hours as the metal disappeared and the liquid turned deep orange. He set the unremarkable beaker on a shelf crowded with other bottles. German officers searched the institute and walked right past it. After the war he returned to find the beaker untouched, precipitated the gold back out of the solution, and sent it to Stockholm — where the Nobel Foundation recast the medals from their original gold and re-presented them in 1952.
Why It Matters
Gold is famous for being hard to change, yet these medals were taken apart with acid and made to look like nothing special. The hiding place was not a secret vault but a plain laboratory shelf, right under the noses of soldiers searching the building. The same chemistry that destroyed the visible medals also made it possible to recover the gold later, because the metal was not lost forever, only dissolved into solution.
Wait — That's Not Quite Right
A common mistake is to think gold cannot be dissolved at all. Pure gold resists many chemicals, but aqua regia is one of the rare mixtures that can break it down. Another wrong idea is that the medals were destroyed forever; in fact, the gold was later precipitated back out, recast, and returned after the war.
Vocabulary
- aqua regia
- nitric acid
- hydrochloric acid
- dissolve
- precipitate
- gold
- nobel medal
- occupied copenhagen
- niels bohr
- laboratory
- solution
- recast
Quick Quiz
5 questions · For classroom or kitchen table
The Experiment
Make a Hidden-Object Shelf Test
Set up a small shelf or tabletop with a few ordinary household bottles, cups, and boxes. Ask a family member or classmate to place a small object, like a paperclip or toy coin, in plain sight among the other items while you wait in another room.
When you return, see how easy or hard it is to spot the object. Then rearrange the scene so the object is more visible, and compare. The point is to notice how something can be hidden without being concealed in a special container, just by blending into an ordinary setting.
For an extra connection to the story, talk about why a plain beaker on a crowded laboratory shelf might not attract attention during a rushed search. Do not use real acids or chemicals for this activity.
small ordinary object, shelf or tabletop, cups or boxes, adult supervision if used in a classroom
Where this came from
- Science History Institute, "The Scientific Way to Fool a Nazi" (on George de Hevesy dissolving the von Laue and Franck medals). https://www.sciencehistory.org/stories/disappearing-pod/the-scientific-way-to-fool-a-nazi/ — corroborated by the AIP and de Hevesy's own account.
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