Water composed of heavy isotopes of hydrogen or oxygen,
or of both; esp. deuterium oxide, D2O, which is water,
composed of ordinary oxygen and deuterium. It is
a colorless liquid, which forms hexagonal crystals
on freezing. Its physical properties differ from
those of normal water.
oxide D2O, occurs to small extent (about 0.003% by
weight) in natural water, from which it can be separated
by fractional distillation or by electrolysis.
is useful in the nuclear industry because of its ability
to reduce the energies of fast neutrons to thermal
energies and because its absorption cross section
is lower than that of hydrogen and consequently it
does not appreciably reduce the neutron flux.
the laboratory it is used for labellin other molecules
for studies of reaction mechanisms.