Deuterium oxide is used as a moderator in heavy water nuclear reactors to reduce the speed of the neutrons released in a nuclear chain reaction. Scientists frequently use deuterium to study organic and biochemical reactions. In a process known as deuterium labeling, the heavy hydrogen atom serves as an isotopic tracer by acting as a substitute for one or more of the regular hydrogen atoms in a molecule. After the reaction is completed, the deuterium can be located by spectroscopic studies. This technique gives scientists important clues as to how the reaction takes place.
Scientists use deuterons as bombarding particles in particle accelerators.
One such device, a cyclotron, can accelerate deuterons to energy levels of millions or even billions of electron volts. Another isotope of hydrogen, called tritium, has an atomic mass of about 3. It contains one proton plus two neutrons, and is unstable. Harold C. Urey, an American chemist, announced his discovery of deuterium in 1932. He distilled liquid hydrogen and detected deuterium in the liquid remaining.