Heavy Water

Common water is called heavy water when there’s the presence of Deuterium in the chemical structure instead of Hydrogen. Water and heavy water carry several different properties. Moreover, there are several types of heavy waters, namely semi-heavy water, heavy oxygen water and treated water. All these waters are prepared by unique methods and used for various purposes. 

About Heavy Water

Heavy water is a type of water that contains Deuterium in place of common Hydrogen, therefore also called Deuterium oxide. Deuterium is an isotope of Hydrogen containing an additional neutron along with the proton, whereas the regular Hydrogen contains only proton. Heavy water is denoted as D₂O or 2H₂O and is slightly heavier than the normal water molecule due to the heavy Hydrogen. 

The normal water obtained from the natural sources consists of about one deuterium atom per 6760 normal hydrogen atoms. Heavy water has a somewhat higher density than normal water. Heavy water is also present in the human body naturally but in a very small amount, thus being harmless. It is an important neutron moderator in nuclear reactions, thus discovered some years before nuclear fission in 1938, in 1932.

Properties of Heavy Water

Heavy water has slightly different properties than normal water. The molecular mass of heavy water is 20.02g/mole and density of about 1.107g/ml. It has a melting point of 3.82⁰C and a boiling point of 101.4⁰C. Heavy water is colourless and odourless liquid at room temperature. Since heavy water has a density heavier than normal water, an ice cube made of heavy water will sink in normal water. At a given temperature, the heavy water is less breakable than normal water. If present in high quantity, it can harm the living cells due to their different solvent properties.

Types of Heavy Water

There are many types of heavy water based on the types of Hydrogen as their constituents.

Semi-Heavy Water

Semi-heavy water is made of one Deuterium, one Oxygen, and one protium instead of the second oxygen atom and is symbolised as HDO. Protium is an isotope of the hydrogen atom that contains one proton and one electron. This is the most common type of heavy water found if there is a mixture of hydrogen isotopes. We can understand this as if a sample contains equal amounts of protium and Deuterium. Then there is a possibility that there is 50% of semi-heavy water, 25% of normal, and 25% of heavy water present in the sample. The three exist in dynamic equilibrium.

Heavy-Oxygen Water

Some water contains heavy isotopes of Oxygen like 17O and 18O, thus called heavy-oxygen water. This type of water is also heavier than normal water. Heavy water is used to trace radioactive isotopes and the production of fluorine 18. The density of such heavy water is more than normal water. Heavy-oxygen water is used in radiopharmaceuticals and as neutron moderators in nuclear reactors.

Tritiated Water

Some heavy water contains another heavier isotope of Hydrogen called tritium, denoted by 3H. this isotope of Hydrogen contains one proton and two neutrons, thus making it denser. Tritium is radioactive in nature and thus is the tritiated water. It is also called super-heavy water and is used to calculate the total amount of water in a body.

Preparation of Heavy Water

Any type of water sample obtained by the natural resources usually has one deuterium atom per 6760 normal hydrogen atoms. Therefore technically, heavy water is not prepared; rather, it is obtained out of the normal water with the help of a heavy water reactor. But the cost of such reactors remains very high. Because of this, nowadays, heavy water is separated through fractional distillation also. It is also prepared by electrolysis of water containing alkali for a long period.

Uses of Heavy Water

The most prominent use of heavy water is as a neutron moderator and coolant in nuclear power plants. Other uses of heavy water include isotropic tracer in many biological and chemical processes like respiration, photosynthesis, etc. It is used in NMR spectroscopy used to study atoms and nuclei. Heavy water is also used to determine the metabolic rate in humans and other animals also.

Conclusion

From all above, we covered various concepts of Heavy water. We learned their preparation, properties, and uses, along with all general information. We can now understand that heavy water is a different form of water with Deuterium present in the chemical structure, making the molecule more heavy and dense. Moreover, we also learned about semi-heavy water, heavy oxygen water and treated water lastly. Heavy waters are essential as they are significantly used in biological and chemical fields for different purposes.