When Nazi-Germany swallowed Europe, the Danish physicist Niels Bohr fought back with the only weapon he had: chemistry.
Niel Bohr transformed into something like Oskar Schindler in a lab coat. From his Institute for Theoretical Physics in Copenhagen, the Nobel laureate aided and protected Jewish scientists, which landed him in hot water in 1940.
The Nazis had attempted to lock down Germany’s gold supply by making exportation of the metal a state crime. During the 1930s, two German physicists, the Jewish James Franck and the outspoken Hitler critic Max von Laue, smuggled their Nobel medals to Bohr’s lab for safekeeping.
The lab made a perfect hiding spot until April 1940 when the Nazis invaded and occupied Copenhagen. They are literally marching through the streets, and Bohr has just hours, maybe minutes, to make two golden Nobel Prize medals disappear. He knew the Germans would confiscate them, and they were not his medals.
Made of 23-karat hold, the medals are heavy to handle, and being shiny and noticeable. Clearly inscribed “Von Laue” (for Max von Laue, winner of the 1914 Prize for Physics) and “Franck” (for James Franck, the physics winner in 1925) — they were like two death warrants.
On the day that the Nazis arrived in Copenhagen, Hungarian radiochemist George de Hevesy was working in Bohr’s lab. They discussed how to hide the medals and thought about burying them at first.
“I suggested we should bury the medals, but Bohr did not like this idea of them being unearthed,” recalls de Hevesy in his autobiography.
“I decided to dissolve them. So while the invading forces were marching down the streets of Copenhagen, I was busy dissolving von Laue and Franck’s medals.”
But the medals would not simply disappear as von Hevesy recalled from his studies how gold is “unreactive and difficult to dissolve”. All the while, the Nazis were getting closer.
Racing against the clock, de Hevesy saved the day by dissolving the bulky gold medals in aqua regia, which is made up of three parts hydrochloric acid and one part nitric acid. When the gold was dropped into the solution, the hydrochloric acid will separate the gold as long as the nitric acid loosens the metals’ atoms. And then it is left to the chloride ions to complete the process.
As you can see in this video from the University of Nottingham, dissolving gold is a slow business.
When the German soldiers pounded on the lab’s door, all which remained of the medals was an inconspicuous bottle of bright orange liquid.
In his book The Disappearing Spoon, the science writer Sam Kean writes:
“When the Nazis ransacked Bohr’s institute, they scoured the building for loot or evidence of wrongdoing but left the beaker of orange aqua regia untouched. Hevesy was forced to flee to Stockholm in 1943, but when he returned to his battered laboratory after V-E Day, he found the innocuous beaker undisturbed on a shelf.”
The flask was untouched.
In 1950, de Hevesy reversed the chemistry by separating the metal from the solution. He then sent the raw metal to the Swedish Academy in Stockholm. The gold was recast into two Nobel Prize medals that were re-presented to Franck and von Laue at reward ceremonies in 1952.
Bohr was also a winner of the Nobel Prize for Physics, but his medal did fortunately not need to be liquified. It had a month before the Occupation been put up for auction to raise money for Finnish Relief. The unknown bidder then donated the medal to the Danish Historical Museum of Fredrikborg, where it still remains.
Danish Nobel Winner Foiled the Führer, compiled by Tor Kjolberg