Abstract

Deuterium (²H or D) the heavier, stable isotope of hydrogen (¹H) occurs in nature, and is always present in all hydrogen-containing compounds. Deuterium oxide, known as heavy water, is the most important deuterium compound. Heavy water differs from ordinary water in structure of the liquid phase, in nuclear spin, ionic equilibria, and in various spectroscopic properties. Kinetic isotope effects occur in chemical reactions involving bond rupture of H and D. This effect in hydrogen exchange between water and hydrogen sulfide is the basis for the most important separation process for large-scale deuterium production. Infrared absorption is the method of choice for the analysis of heavy water. Deuterium has far-reaching biological effects, and it is possible to grow living organisms in which all of the hydrogen normally present is replaced by deuterium. The nuclear properties of deuterium are such that heavy water is the most efficient neutron moderator known for nuclear fission reactors. Deuterium is also important in nuclear fusion technology.

Tritium (³H or T) is the heaviest isotope of hydrogen. Unlike hydrogen or deuterium, T undergoes radioactive decay (B^–, ~ 12 yr half-life). Thus T compounds experience radiation damage at elevated tritium levels. Tritium is produced by cosmic rays in the higher atmosphere, and by neutron capture in lithium–aluminum alloy in nuclear fission reactors. Tritium can be purified by distillation, by thermal diffusion, by diffusion through palladium-silver-nickel membranes, or by chromatography on coated molecular sieves. Tritium is widely used as a tracer in molecular biology experiments. Tritium is a key element in nuclear fusion, in which energy is produced by the controlled fusion of tritium with deuterium.