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.
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| Names | |||
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| IUPAC name
(O-2H1)Water
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| Other names
Deuterium hydrogen monoxide
Deuterium hydrogen oxide, Water-d1, Water-d | |||
| Identifiers | |||
3D model (JSmol)
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| ChEBI | |||
| ChemSpider | |||
| 115 | |||
PubChem CID
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CompTox Dashboard (EPA)
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| 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).
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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
editOn 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
editReferences
edit- ^ Tashakor S (2016-09-28). "Neutronic Investigation of Semi-Heavy Water Application in Hplwr New Flow Pattern". CNL Nuclear Review: 1–5. doi:10.12943/CNR.2016.00019.
- ^ Goncharuk VV, Kavitskaya AA, Romanyukina IY, Loboda OA (June 2013). "Revealing water's secrets: deuterium depleted water". Chemistry Central Journal. 7 (1): 103. doi:10.1186/1752-153X-7-103. PMC 3703265. PMID 23773696.
- ^ "Heavy water | chemical compound". Encyclopedia Britannica. Retrieved 2019-04-24.
- ^ Craig, H.; Gordon, L. I.; Horibe, Y. (1963). "Isotopic exchange effects in the evaporation of water: 1. Low-temperature experimental results". Journal of Geophysical Research. 68 (17): 5079–5087. Bibcode:1963JGR....68.5079C. doi:10.1029/JZ068i017p05079.
Further reading
edit- Schwarzer D, Lindner J, Vöhringer P (October 2005). "Energy relaxation versus spectral diffusion of the OH-stretching vibration of HOD in liquid-to-supercritical deuterated water". The Journal of Chemical Physics. 123 (16): 161105. Bibcode:2005JChPh.123p1105S. doi:10.1063/1.2110087. hdl:11858/00-001M-0000-0012-E7B7-2. PMID 16268674.
