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Heavy Water

Physics and Chemistry of Water

  1. Gholam A. Kazemi

Published Online: 15 APR 2005

DOI: 10.1002/047147844X.pc266

Water Encyclopedia

Water Encyclopedia

How to Cite

Kazemi, G. A. 2005. Heavy Water. Water Encyclopedia. 4:462–466.

Author Information

  1. Shahrood University of Technology, Shahrood, Iran

Publication History

  1. Published Online: 15 APR 2005


Each of the atoms of hydrogen and oxygen, which form the water molecule, has three isotopes; 1H, 2H (D), 3H (T) for hydrogen and 16O, 17O, and 18O for oxygen.

The abundances of these isotopes in the hydrosphere, biosphere, and lithosphere and in different stages of the water cycle vary slightly from these figures.

Considering the six isotopes of hydrogen and oxygen, 18 combinations of H[BOND]O[BOND]H or “18 varieties of water” are possible (2, 3).

Of the above eighteen varieties of waters, 1H216O has a mass of 18 and is the most common; it is generally known as “water” or sometime called ordinary or light water. Deuterium oxide (D216O) has a mass of 20 and is known as “heavy water.” Some references use the term “semiheavy water” for HD16O. Washburn and Urey (4) were the first to enrich deuterium oxide in water in 1932. Some of the 18 varieties of water are extremely rare. An interesting, though trivial, point is that the molecular weight of the most common form of water 1H216O (18), equals the number of different varieties of water, 18.


  • water;
  • reactor;
  • isotopic enrichment;