Semi Heavy Water (HDO)

Regular water is composed of two protium isotopes of hydrogen and oxygen. Semi water contains one protium and one deuterium in its composition. It should not be confused with heavy water, where two deuterium hydrogen isotopes are mixed with oxygen.

Isotopes Of Hydrogen And Water

Hydrogen mainly contains three isotopes – protium, deuterium, and tritium. Isotopes are the different forms of the same element with different neutron numbers. All of these isotopes have different properties due to the change in the number of neutrons. There are different types of heavy water based on the isotope of hydrogen present in it.

Semi-Heavy Water

• Semi-heavy water is somewhat between ordinary water and hard water

• It is denoted as HDO

• It has both protium and deuterium as hydrogen components (50-50)

• It is more abundant in heavy water than pure D2O and H2O.

Heavy Oxygen Water

• It contains heavy isotopes of oxygen

• It is used in Positron-Emission Tomography (PET)

• Used in DNA stable isotope probing

• Used in secondary ion mass spectrometry

• Used in plant ecology

Tritiated Water

• It is a form of water with tritium as a hydrogen component

• It is radioactive

• Hazardous when inhaled, ingested, and absorbed through the skin

• It is denoted as HTO 

• When it is used with phosphorus, it glows in the dark. This is utilised in signboards.

• Found in nuclear weapon

• Used as a radioactive tracer

• Detected by liquid scintillation counting

Semi-Heavy Water

It is denoted as HDO. Semi-heavy water exhibits equal characteristics of protium and deuterium. Other chemical names of semi-heavy water include deuterium hydrogen monoxide and deuterium hydrogen oxide. In normal water, there will be protium and deuterium isotopes. 

These isotopes are rapidly exchanged between water molecules. So there will be light water, heavy water, and semi-heavy water in heavy water. But while calculating the abundance, it is found that semi-heavy water composition is more in heavy water. Several studies have been carried out testing semi-heavy water as a moderator in reactors. 

But it will cause neutrons to travel a longer distance and reduce thermal neutron flux. So using semi-heavy water as a moderator might not be a good idea.

Structure Of Semi-Heavy Water

Properties Of Semi-Heavy Water

As we mentioned earlier, there will be a slight difference in the properties of water due to a change in the number of neutrons between isotopes.

• Physical properties like melting point, boiling point etc., will have higher values than normal water.

• Chemical reactions take place at a slow pace when compared to normal water. 

Brief About Heavy Water

Heavy water is a form of water with a deuterium composition. Deuterium is a hydrogen isotope with two neutrons; D2O is the symbol for it. Due to the heavier deuterium, this will have different nuclear characteristics than a regular H atom. The human body contains a small quantity of heavy water by nature. A huge volume of heavy water might make a healthy human body sick. 

Multiple steps of electrolysis separate the deuterium found naturally in water. The deuterium was then extracted and interacted with oxygen to form heavy water. The girdler sulphide method also creates heavy water. The boiling temperature, freezing point, and density of heavy water are all somewhat greater than those of ordinary water.

Conclusion

Two protium isotopes of hydrogen and oxygen compose regular water. Semi water contains one protium and one deuterium. Semi-water is not the same as heavy water. Semi-heavy water exhibits equal characteristics of protium and deuterium. 

Deuterium hydrogen monoxide and deuterium hydrogen oxide are the other chemical names for semi-heavy water. In normal water, there will be protium and deuterium isotopes, which are rapidly exchanged between water molecules. So there will be light water, heavy water, and semi-heavy water in normal water. But when calculating the abundance, it is found that semi-heavy water composition is more in regular water.

There have been several studies carried out to test semi-heavy water as a moderator in reactors. It was found to cause neutrons to travel a longer distance and reduce thermal neutron flux. So using semi-heavy water as a moderator is probably not a good idea.