Deuterium

Deuterium is a stable isotope of hydrogen with a relative atomic mass of 2.014102 compared to the atomic mass of protium, 1.007825. Deuterium occurs to the extent of about 0.0156% in a sample of naturally occurring hydrogen. Its melting point is -426°F (-254°C)—compared to -434°F (-259°C) for protium—and its boiling point is -417°F (-249°C)–compared to -423°F (-253°C) for protium. Its macroscopic properties of color, odor, taste, and the like are the same as those for protium.

Compounds containing deuterium have slightly different properties from those containing protium. For example, the melting and boiling points of heavy water are, respectively, 38.86°F (3.81°C) and 214.56°F (101.42°C). In addition, deuterium bonds tend to be somewhat stronger than protium bonds. Thus chemical reactions involving deuterium-containing compounds tend to go more slowly than do those with protium.

Deuterium is now prepared largely by the electrolysis of heavy water, that is, water made from deuterium and oxygen (D₂O). Once a great rarity, heavy water is now produced rather easily and inexpensively in very large volumes.