Deuterium

Contributed by Microsoft Encarta

Deuterium, stable, nonradioactive isotope of hydrogen with atomic wt. 2.01363 and symbol D, or 2H2. It is commonly
called heavy hydrogen because its atomic weight is approximately double that of ordinary hydrogen, but it has
identical chemical properties. Hydrogen as it occurs in nature contains approximately 0.02 percent of deuterium. The
boiling point of deuterium is -249.49° C (-417.08° F), or 3.28° C (5.90° F) higher than that of hydrogen. Heavy water
(deuterium oxide, D2O) boils at 101.42° C (214.56° F) as compared to 100° C (212° F), the boiling point of ordinary
water. It freezes at 3.81° C (38.86° F) as compared to 0° C (32° F) for ordinary water. Its density at room temperature
is 10.79 percent greater than that of ordinary water.

Deuterium, which was discovered by the American chemist Harold Urey and his associates in 1932, was the first isotope to
be separated in a pure form from an element. Several methods have been used to separate the isotope from natural hydrogen.
The two processes that have been most successful have been fractional distillation of water and a catalytic exchange process
between hydrogen and water. In the latter system, when water and hydrogen are brought together in the presence of a suitable
catalyst, about three times as much deuterium appears in the water as in hydrogen. Deuterium has also been concentrated by
electrolysis, centrifuging, and fractional distillation of liquid hydrogen. The nuclei of deuterium atoms, called deuterons,
are much used in research in physics because they can be readily accelerated by cyclotrons and similar machines and used as
"atomic bullets" to transmute elements. Deuterium also has important uses in biological research as a tracer element for
studying problems of metabolism (see ISOTOPIC TRACER). The use of heavy water as a moderator in atomic piles was suggested
during World War II but in the first U.S. piles, graphite was employed instead (see NUCLEAR ENERGY). Deuterium, either in
deuterium oxide or in lithium deuteride (LiD), and tritium are essential components of nuclear fusion weapons, or hydrogen
bombs (see NUCLEAR WEAPONS).