Semiheavy water is the result of replacing one of the protium in normal water with deuterium.[1] It exists whenever there is water with light hydrogen (protium, 1H) and deuterium (D or 2H) in the mix. This is because hydrogen atoms (1H and 2H) are rapidly exchanged between water molecules. Water containing 50% 1H and 50% 2H, is about 50% H2HO and 25% each of H2O and 2H2O, in dynamic equilibrium.[2] In normal water, about 1 molecule in 3,200 is HDO (one hydrogen in 6,400 is 2H). By comparison, heavy water D2O[3] occurs at a proportion of about 1 molecule in 41 million (i.e., one in 6,4002). This makes semiheavy water far more common than "normal" heavy water.

Quick Facts Names, Identifiers ...
Semiheavy water
Thumb
Spacefill model of water
Thumb
Names
IUPAC name
(O-2H1)Water
Other names
Deuterium hydrogen monoxide
Deuterium hydrogen oxide, Water-d1, Water-d
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
115
  • InChI=1S/H2O/h1H2/i/hD
    Key: XLYOFNOQVPJJNP-DYCDLGHISA-N
  • [2H]O
Properties
H2HO or HDO
Molar mass 19.0214 g mol−1
Appearance Very pale blue, transparent liquid, very similar to regular water
Density 1.054 g cm−3
Melting point 3.81 °C (38.86 °F; 276.96 K)
Boiling point 100.74 °C (213.33 °F; 373.89 K)
miscible
log P −0.65
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Close

The freezing point of semiheavy water is close to the freezing point of heavy water at 3.8°C compared to the 3.82°C of heavy water.

Production

On Earth, semiheavy water occurs naturally in normal water at a proportion of about 1 molecule in 3,200. This means that 1 in 6,400 hydrogen atoms in water is deuterium, which is 1 part in 3,200 by weight (hydrogen weight). The HDO may be separated from normal water by distillation or electrolysis and also by various chemical exchange processes, all of which exploit a kinetic isotope effect, with the partial enrichment also occurring in natural bodies of water under particular evaporation conditions.[4] (For more information about the isotopic distribution of deuterium in water, see Vienna Standard Mean Ocean Water.)

See also

References

Further reading

Wikiwand in your browser!

Seamless Wikipedia browsing. On steroids.

Every time you click a link to Wikipedia, Wiktionary or Wikiquote in your browser's search results, it will show the modern Wikiwand interface.

Wikiwand extension is a five stars, simple, with minimum permission required to keep your browsing private, safe and transparent.