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Heavy water

Heavy water
Spacefill model of heavy water
Names
IUPAC name
[2H]2-Water
Other names
  • Deuterium oxide
  • Water-d2
  • Dideuterium monoxide
Properties
D
2O
Molar mass 20.0276 g mol−1
Appearance Very pale blue, transparent liquid
Odor Odorless
Density 1.107 g mL−1
Melting point 3.82 °C; 38.88 °F; 276.97 K
Boiling point 101.4 °C (214.5 °F; 374.5 K)
Miscible
log P −1.38
1.328
Viscosity 1.25 mPa s (at 20 °C)
1.87 D
Hazards
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazards (white): no codeNFPA 704 four-colored diamond
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YesYN ?)
Infobox references

Heavy water (deuterium oxide, 2
H
2O) is a form of water that contains a larger than normal amount of the hydrogen isotope deuterium (2
H or D, also known as heavy hydrogen), rather than the common hydrogen-1 isotope (1
H or H, also called protium) that makes up most of the hydrogen in normal water. The presence of deuterium gives the chemical different nuclear properties, and the increase of mass gives it different physical and chemical properties compared to normal "light water".

Deuterium is a hydrogen isotope with a nucleus containing a neutron and a proton; the nucleus of a protium (normal hydrogen) atom consists of just a proton. The additional neutron makes a deuterium atom roughly twice as heavy as a protium atom.

A molecule of heavy water has two deuterium atoms in place of the two protium atoms of ordinary "light" water. The weight of a heavy water molecule, however, is not substantially different from that of a normal water molecule, because about 89% of the molecular weight of water comes from the single oxygen atom rather than the two hydrogen atoms. The colloquial term heavy water refers to a highly enriched water mixture that contains mostly deuterium oxide D
2O, but also some hydrogen-deuterium oxide (HDO) and a smaller number of ordinary hydrogen oxide H
2O molecules. For instance, the heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction—meaning that 99.75% of the hydrogen atoms are of the heavy type. For comparison, ordinary water (the "ordinary water" used for a deuterium standard) contains only about 156 deuterium atoms per million hydrogen atoms, meaning that 0.0156% of the hydrogen atoms are of the heavy type.


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