Heavy Water, D2O

"Francis Aston (photo, right) found evidence for the existence of isotopes in 1913, and he published his findings in 1920. Aston was awarded the Nobel prize for Chemistry in 1922. Soon after, Rutherford suggested the existence of a heavier isotope of hydrogen, which we now call deuterium. It was first detected in 1931 by Harold Clayton Urey (see photo, below), who found that he could enrich liquid hydrogen somewhat by fractional distillation, and confirmed the cause of weak lines in the atomic spectrum of samples of hydrogen as due to the presence of small amounts of deuterium. Using electrolysis, Urey succeeded in enriching samples of water in the heavier isotope. The next step was to isolate pure heavy water. Along with his student Ronald T. MacDonald, the great American chemist Gilbert Newton Lewis (1875-1946) set to the task, using both electrolysis and fractional distillation under reduced pressure (employing a 72-feet-high distillation column). Armed with his supply of deuterium oxide, Lewis set out to investigate its properties - not just the obvious ones, like melting and boiling points - but also whether it would support life (a white mouse drank it and came back for more)."