Harold Urey discovered the isotope deuterium in 1931 and was later able to concentrate it in water. Urey's mentor Gilbert Newton Lewis isolated the first sample of pure deuterium oxide (heavy water) by electrolysis in 1933. George de Hevesy and Erich Hofer used heavy water in 1934 in one of the first biological tracer experiments, to estimate the rate of turnover of water in the human body. Emilian Bratu and Otto Redlich studied the auto dissociation of deuterium oxide in 1934.
Fig 1. Harold Urey discoverer of the deuterium
Source:
https://en.wikipedia.org/wiki/Heavy_water
