Portrait of Harold Clayton Urey (1893-1981) American physical chemist and discoverer of deuterium. Urey originally trained in zoology, later turning to chemistry. In 1931 he started research into 'heavy hydrogen'. He used the different partial pressures of the two isotopes to isolate heavy hydrogen, now named deuterium. This work won him the 1934 Nobel Prize for Chemistry. He then used similar techniques to obtain other isotopes of other elements, notably carbon and nitrogen. His process was modified in WW2 to produce the enriched uranium for the first atom bomb. After this, Urey turned to geophysics, and campaigned vigorously against nuclear weapons.