Tritiated water

Tritiated water is a form of water where the usual hydrogen atoms are replaced with tritium

Tritium

Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...

. In its pure form it may be called tritium oxide (T₂O or ³H₂O) or super-heavy water. Pure T₂O is corrosive

Corrosive

A corrosive substance is one that will destroy or irreversibly damage another surface or substance with which it comes into contact. The main hazards to people include damage to the eyes, the skin, and the tissue under the skin; inhalation or ingestion of a corrosive substance can damage the...

 due to self-radiolysis

Radiolysis

Radiolysis is the dissociation of molecules by nuclear radiation. It is the cleavage of one or several chemical bonds resulting from exposure to high-energy flux...

. Diluted, tritiated water is mainly H₂O plus some HTO (³HOH). It is also used as a tracer for water transport studies in life-science research. Furthermore, since it naturally occurs in minute quantities, it can be used to determine the age of various water-based liquids, such as vintage wines.

It should not be confused with heavy water

Heavy water

Heavy water is water highly enriched in the hydrogen isotope deuterium; e.g., heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction...

, which is deuterium oxide.

Applications

Tritiated water can be used to measure the total volume of water in one's body

Body water

In medicine, body water is the water content of the human body. A significant fraction of the human body is water. Arthur Guyton 's Textbook of Medical Physiology states that "the total amount of water in a man of average weight is approximately 40 litres, averaging 57 percent of his total body...

. Tritiated water distributes itself into all body compartments relatively quickly. The concentration of tritiated water in urine

Urine

Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...

is assumed to be similar to the concentration of tritiated water in the body. Knowing the original amount of tritiated water that was ingested and the concentration, one can calculate the volume of water in the body.

• Amount of tritiated water (mg) = Concentration of tritiated water (mg/ml) x Volume of body water (ml)

• Volume of body water (ml) = [Amount of tritiated water (mg) - Amount excreted (mg)] / Concentration of tritiated water (mg/ml)