Heavy water

Heavy water, or deuterium oxide (D₂O), chemical compound that occurs as 0.014% of ordinary water, which it closely resembles. It is used as a moderator in nuclear reactors and as a source of deuterium and its compounds. It is toxic in high concentrations. Heavy water freezes at 38.8°F (3.8°C) and boils at 214.5°F (101.4^oC). Water containing tritium or heavy isotopes of oxygen (¹⁷O and ¹⁸O) is also called heavy water.

See also: Deuterium.