Heavy water is a form of water that contains a larger than normal amount of the hydrogen isotope deuterium, rather than the common hydrogen-1 isotope that makes up most of the hydrogen in normal water.
Formula: D2O
IUPAC ID: [2H]2-water
Molar mass: 20.0276 g/mol
Boiling point: 101.4 °C
Melting point: 3.8 °C
Refractive index (nD): 1.328

