Today's episode: How Acid Foiled the Nazis!

In early 1940, Nazi Germany was poised to invade Denmark. Danish scientists Neils Bohr and George de Hevesy ran a laboratory institute in Copenhagen which doubled as a haven for Jewish refugees. Bohr was in possession of two solid gold Nobel Prize medals that had been awarded in 1914 and 1925 to Jewish German physicists who had fled Germany prior to the war. Bohr himself had won a Nobel Prize in 1922. Aware that the medals bore the names of the recipients, and would certainly be coveted and sent back to the coffers of the Third Reich, Bohr took action.

A month before the invasion, he destroyed all records of any refugees he'd employed or sheltered, then gave his own Nobel medal to a Finnish non-profit, which held an auction. The anonymous buyer held onto the medal until after the war, then donated it back to the Danish government. The question of what to do with the refugees' medals was more difficult to answer. They'd been entrusted to Bohr and he felt uneasy giving them away, and rejected de Hevesy's idea of burying them (where they might still fall into the hands of the Third Reich). They needed a better solution.

The solution they came up with, literally at the last minute, was just that — a solution. Nitrohydrochloric acid! As the occupying Nazi army strode into Copenhagen, de Hevesy combined three parts hydrochloric acid with one part nitric acid — a solution called aqua regia, Latin for "regal water," which is capable of wholly dissolving pure gold. Both Nobel Prize medals were dropped in the solution and dissolved; the container was capped and placed on a shelf with other similar solutions.

SS officials raided the lab minutes later and questioned both men on their activities. The medals, now aqueous and suspended in solution, escaped detection. After the war, de Hevesy took the container and boiled off the acid solution and reduced the contents to a fine powder of pure gold precipitate — a common process for the refinement of .999 fine gold bars and bricks. He returned the powder to the Nobel Institute, which reconstituted the gold, recast the medals, and awarded them again.

And so, chemistry foiled the Nazis! Stay tuned for the next Adventures in Chemistry!