IN APRIL 1940, the celebrated physicist Niels Bohr was in a quandary: what to do with two gold Nobel medals, given to him for safe keeping at the Institute of Theoretical Physics in Copenhagen. With Nazi forces invading Denmark, it was only a matter of time before the institute was searched.
After rejecting the idea of burying the medals, Bohr and his colleague George de Hevesy dissolved them in a mixture of nitric and hydrochloric acid. They poured the resulting orange liquid into two bottles and placed them, in plain view, on a laboratory shelf. Years later, the gold was…
