Denis kondaborav
Harmless
Posts: 11
Registered: 8-1-2018
Member Is Offline
Mood: No Mood
|
|
Heavy water
Can i extract heavy water by freezing tap water to 3 degrees 37 fahrenheit
|
|
|
zed
International Hazard
Posts: 2283
Registered: 6-9-2008
Location: Great State of Jefferson, City of Portland
Member Is Offline
Mood: Semi-repentant Sith Lord
|
|
Probably not. But, it is an interesting idea.
Seems like I read somewhere, that there are deep ocean currents that are rich in heavy water.
Also, that comets and asteroids may be "enriched".
I was under the impression, that it is usually acquired by electrolysis.
|
|
|
aga
Forum Drunkard
Posts: 7030
Registered: 25-3-2014
Member Is Offline
|
|
What did your geiger counter read when you tried it ?
Did you see an increase in radioactivity ?
|
|
|
JJay
International Hazard
Posts: 3440
Registered: 15-10-2015
Member Is Offline
|
|
Heavy water isn't radioactive.
|
|
|
aga
Forum Drunkard
Posts: 7030
Registered: 25-3-2014
Member Is Offline
|
|
Really ? i thought a deuterium-rich mix was radioactive.
Bummer.
|
|
|
phlogiston
International Hazard
Posts: 1379
Registered: 26-4-2008
Location: Neon Thorium Erbium Lanthanum Neodymium Sulphur
Member Is Offline
Mood: pyrophoric
|
|
Deuterium is stable, but processes used to purify deuterium usually also increase the concentration of tritium, which is radioactive.
However, the amounts are still very tiny. The beta radiation emitted by tritium is also of such a low energy that a common Geiger counter won't
measure anything.
[Edited on 28-1-2018 by phlogiston]
-----
"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
|
|
Texium
|
Thread Moved
29-1-2018 at 16:05 |
Vomaturge
Hazard to Others
Posts: 286
Registered: 21-1-2018
Member Is Offline
Mood: thermodynamic
|
|
Apparently, there are many processes that favor deuterium over normal hydrogen (or vice versa), but not all of them are capable of shifting
concentrations by more than a few percent. One of the most common ones involves molecules of hydrogen sulfide exchanging their hydrogen atoms with
water molecules
http://pubs.acs.org/doi/pdf/10.1021/bk-1978-0068.ch001
The way I understand this (and I don't understand it too well) the deuterium has a better chance (relative to normal hydrogen) of being transferred to
the H2S at elevated temperatures, and a better chance of being transferred back into the water at cooler temperatures. By cycling H2O and H2S
appropriately, a good concentration of deuterium can be built up in both. On page 21 of this paper, there is a graph showing the energy use and
separation factor for different heavy water concentration methods. "H2O crystallization" is included in the graph, and it looks like it only increases
the heavy water concentration in the ice by a percent or two. So, freezing does work, but it might only boost the concentration from say, 150 ppm to
153 ppm. I would expect the temperature for this to work would be closer to the freeze point of "normal" water. Mixtures often behave strangely as far
as melting point. Salt melts at around 800C, ice melts at 0C, but mixtures of salt and ice melt at temperatures below 0C. I'm not sure how it would
work with varying isotopes of the same element, but it seems that pure D2O cannot be frozen out of normal water by cooling it to a temperature between
the melting points of H2O and D2O. That's too bad, since a fractional freeze distillation would be very safe, straightforward, energy efficient, and
easy to do at home.
|
|
|
unionised
International Hazard
Posts: 5126
Registered: 1-11-2003
Location: UK
Member Is Offline
Mood: No Mood
|
|
Heavy water has a freezing pint a little higher than ordinary water.
Imagine something that has a freezing point much higher than that of water.
Like salt- which melts near 800C.
If you add a little salt to water (to mimic the fact that there's only a little heavy water in normal water) and cooled it below 800C would all the
salt "freeze" out?
Obviously not.
Well, in the same way, heavy ice will dissolve in ordinary water at 3C.
So cooling water to 3C will not get you any heavy ice.
Sorry.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
