Heavy Water (redirected from Semiheavy water)

heavy water: see deuterium.

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heavy water

 or deuterium oxide

Water composed of two atoms of deuterium (D; a heavy isotope of hydrogen) and one atom of oxygen (O), chemical formula D₂O. Water from most natural sources contains about 0.015% deuterium oxide; this can be enriched or purified by distillation, electrolysis, or chemical processing. Heavy water is used as a moderator in nuclear power plants, slowing down the fast neutrons so that they can react with the fuel in the reactor. Heavy water is also used in research as an isotopic tracer for chemical reactions and biochemical pathways. Water with tritium (T₂O) rather than deuterium may also be called heavy water.

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heavy water

water that has been electrolytically decomposed to enrich it in the deuterium isotope in the form HDO or D₂O - PLEASE CHECK FORMULA

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heavy water [′hev·ē ′wȯd·ər]

(inorganic chemistry)

A compound of hydrogen and oxygen containing a higher proportion of the hydrogen isotope deuterium than does naturally occurring water. Also known as deuterium oxide.

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Heavy Water 

D₂O, an isotopic species of water in which the light hydrogen atom ¹H is replaced by its heavy isotope ²H, which is called deuterium (D).

Heavy water was first discovered in natural water by H. Urey and E. F. Osborn (USA) in 1932; the species was isolated by G. N. Lewis and R. MacDonald (USA) in 1933. The density of heavy water is greater than that of ordinary water, hence the name. Heavy water is found in natural water and in atmospheric precipitation in the ratio of one D atom to 5,000–7,000 H atoms. The techniques of mass spectrometry, densimetry, and infrared spectroscopy are used in determining the content of heavy water.

The physical properties of D₂O differ markedly from those of H₂O. Heavy water boils at 101.43°C and freezes at 3.82°C; its density is 1.104 g/cm³. The chemical properties of heavy water are very close to those of H₂O, although certain reactions occurring in a D₂O medium are retarded or accelerated, sometimes by a factor between 2 and 3. The principal industrial methods for producing heavy water are the isotopic exchange of water and hydrogen sulfide, the distillation of hydrogen, and multistep electrolysis.

Heavy water is used in nuclear physics and power engineering as a neutron moderator and heat-transfer agent in nuclear reactors; it also serves as a starting material in the production of deuterium. Heavy water is used in chemistry, biology, and hydrology as an isotope tracer. In organisms, even a small amount of heavy water has an inhibitory effect, while larger doses are lethal.

The term “heavy water” is also used for water containing heavy oxygen, where ¹⁶O has been replaced by the heavy isotopes ¹⁷O and ¹⁸O. It likewise applies to HDO, to tritiated water (T₂O), and to HTO and DTO. In superheavy water, ‘H is replaced by the radioisotope ³H, known as tritium (T).

REFERENCES

Kirshenbaum, I. Tiazhelaia voda. Moscow, 1953. (Translated from English.)
Kirshenbaum, I. Proizvodstvo tiazheloi vody. Moscow, 1961. (Translated from English.)
Kratkaia khimicheskaia entsiklopediia, vol. 1. Moscow, 1961. Pages 614–17.
Brodskii, A. I. Khimiia izotopov, 2nd ed. Moscow, 1957.

V. S. PARBUZIN