Spoiler! :
A Nobel Endeavour
In Copenhagen, April 1940, the Hungarian scientist George de Hevesy performed one of the most interesting chemical experiments of the war. The Bohr Institute had received two contraband items: the Nobel Prizes of two German scientists. At the time it was a greivous crime to send gold out of Germany and the two men had sent their medals to the Bohr Institute to prevent them falling into Nazi hands. But now the German army was at the gate and de Hevesy took charge of concealing the medals.
His first solution was to bury them, but Niels Bohr worried that the medals could be unearthed and so de Heversy suggested something a little more audacious: he decided to dissolve them.
Of course gold is notoriously difficult to dissolve – its inertness makes it, appropriately, a member of the “noble metals”. de Hevesy knew it would take a powerful concoction to coerce the gold into solution, so he prepared a solution of Aqua Regia to do the job.
This “royal water” is a mixture of not one, but two acids – one part nitric acid to three parts hydrochloric acid. The nitric acid is able to prise a few gold atoms from the surface of the metal so the hydrochloric acid can strike and trap them in solution as AuCl4- (chloroauride ions). This gradual trickle of gold atoms into solution is not a rapid process, but for de Hevesy it must have been agonisingly slow.
In fact de Hevesy was still dissolving the medals as the German army marched in the streets of Copenhagen, but his perseverence paid off. He sealed the flask and left the orange solution on a high shelf in the laboratory where he could only hope it would remain. When de Hevesy returned to the lab, after the war, he was amazed to find the flask undisturbed.
Fortunately the medals were not locked in solution forever – de Hevesy was able to precipitate out the gold, by neutralising the acid, and returned the raw material to the Nobel Committee. In1950 the medals were recast using the original gold and returned to their rightful owners, all thanks to the ingenuity of George de Hevesy.
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