Physical Properties (with Comparison To Light Water)
| Property | D2O (Heavy water) | HDO (Semiheavy water) | H2O (Light water) |
|---|---|---|---|
| Freezing point (°C) | 3.82 | 0.0 | |
| Boiling point (°C) | 101.4 | 100.7 | 100.0 |
| Density at STP (g/mL) | 1.1056 | 1.054 | 0.9982 |
| Temp. of maximum density (°C) | 11.6 | 4.0 | |
| Dynamic viscosity (at 20 °C, mPa·s) | 1.2467 | 1.1248 | 1.0016 |
| Surface tension (at 25 °C, μJ) | 7.187 | 7.193 | 7.198 |
| Heat of fusion (cal/mol) | 1,515 | 1,436 | |
| Heat of vaporisation (cal/mol) | 10,864 | 10,757 | 10,515 |
| pH (at 25 °C) | 7.43 (sometimes "pD") | 7.266 (sometimes "pHD") | 6.9996 |
| Refractive index (at 20 °C, 0.5893 μm) | 1.32844 | 1.33335 |
Physical properties obvious by inspection: Heavy water is 10.6% denser than ordinary water, a difference which is not immediately obvious. One of the few ways to demonstrate heavy water's physically different properties without equipment is to freeze a sample and drop it into normal water (it will sink). If the water is ice-cold the higher melting temperature of heavy ice can also be observed – it melts at 3.8 °C, and thus holds up very well in ice-cold normal water.
An early experiment reported not the "slightest difference" in taste between ordinary and heavy water; on the other hand, rats given a choice between distilled normal water and heavy water were able to avoid the heavy water based on smell, and it may be possible that it has a different taste.
No physical properties are listed for "pure" semi-heavy water, because it is unstable as a bulk liquid. In the liquid state, a few water molecules are always in an ionised state, which means the hydrogen atoms can exchange among different oxygen atoms. Semi-heavy water can be created by a chemical method but would rapidly transform into a dynamic mixture of 25% light water, 25% heavy water, and 50% semi-heavy water (however if it were made in the gas phase and directly frozen to a solid, this semiheavy ice would be stable).
Read more about this topic: Heavy Water
Famous quotes containing the words physical, properties, comparison and/or light:
“One of the most horrible, yet most important, discoveries of our age has been that, if you really wish to destroy a person and turn him into an automaton, the surest method is not physical torture, in the strict sense, but simply to keep him awake, i.e., in an existential relation to life without intermission.”
—W.H. (Wystan Hugh)
“A drop of water has the properties of the sea, but cannot exhibit a storm. There is beauty of a concert, as well as of a flute; strength of a host, as well as of a hero.”
—Ralph Waldo Emerson (1803–1882)
“In comparison to the French Revolution, the American Revolution has come to seem a parochial and rather dull event. This, despite the fact that the American Revolution was successful—realizing the purposes of the revolutionaries and establishing a durable political regime—while the French Revolution was a resounding failure, devouring its own children and leading to an imperial despotism, followed by an eventual restoration of the monarchy.”
—Irving Kristol (b. 1920)
“She said, “as the light on the dashboard ran
Along the bushes at the roadside a man’s face.
You must have seen it too.””
—Robert Frost (1874–1963)