Water with tritium in it is called tritium oxide. Deuterium and tritium oxide are both poisonous. Even though deuterium isn’t radioactive, Sigma-Aldrich’s MSDS for D[sub]2[/sub]O sounds pretty bad. Heavy water is used in biochemistry to depolymerize microtubules, among other things.
As for how to purify either one, you can do it in your kitchen. If you run a current through ordinary water that contains an electrolyte, hydrogen gas will be evolved at one of the electrodes. It happens that hydrogen-1 turns into hydrogen gas a lot more readily than deuterium or tritium when you electrolyze water, so what’s left behind in the cell is enriched in both. Since the water molecules in the cell are all falling apart and coming back together all the time, and all the light hydrogen is being removed, you end up with a lot of D[sub]2[/sub]O if you let the process run long enough. And if you do this with table salt as the electrolyte, you will discover the answer to the question someone asked in another thread about making chlorine gas.
Well, you start by isolating the HDO (it’s heavier than H[sub]2[/sub]O, so you just wait for it to settle out, sort of). Through dissociation (see above), you get some H+ ions, some D+ ions, and some O - - ions in equal proportions. When they recombine, statistics tells you that if you pick two of the positive ions at random, half the time you’ll get an H and a D, a quarter of the time you’ll get two H’s, and a quarter of the time you’ll get two D’s. So by the simple expedient of waiting, a quarter* of your HDO will turn into D[sub]2[/sub]O and a quarter will turn into H[sub]2[/sub]O. Throw the latter back into the lake, bottle up the former and sell it.
*But you normally won’t wait that long, I bet. Even 1% D[sub]2[/sub]O would give you enough to sell.
OK, I need explanations of the MSDS and the hygroscopic bits. Oh, MS Bookshelf does have hygroscopic. So it’s “able to absorb moisture from the air.” As previously stated, “duh.”
Is this important because it dilutes your heavy water?
And why is heavy water so important for nuclear reactions? Something about “it slows down the neutrons.” Why? And why are these neutrons being spat out? I don’t remember any decay that makes this happen. Is this only when under bombardment?
As far as I know, the problem with heavy water being hygroscopic is, as Dave put it, just that it gets diluted if you expose it to the air.
The reason (or maybe there’s more than one) it’s useful in nuclear reactors is that the neutrons that come from fissioning nuclei have to go on to interact with other nuclei and cause them to fission so you can have a chain reaction. If you slow the neutrons down, it makes them more likely to interact with the fissionable nuclei around them instead of just flying out of the reactor.
Exactly, but a minor nitpick. You would never have O[sup]-2[/sup] in solution, only OH[sup]-[/sup] and OD[sup]-[/sup]. Also, you would never have H[sup]+[/sup] or D[sup]+[/sup] in solution, just H[sub]3[/sub]O[sup]+[/sup], H[sub]2[/sub]DO[sup]+[/sup], HD[sub]2[/sub]O[sup]+[/sup], and D[sub]3[/sub]O[sup]+[/sup]. But the reasoning is all correct. The HDO would be swapping protons and deuteriums like crazy until you’d get a jumbled mess of HDO, D[sub]2[/sub]O, and H[sub]2[/sub]O.
I agree that the main issue here seems to be different interpretations rather than questions of fact. However, quantum mechanics puts some limits on which interpretations are meaningful. Sub-atomic particles are indistinguishable. There is no way, even in principle, to keep track of which proton goes where. If you and I throw a ball at each other, and the balls hit, and we each go pick up a ball, it’s a fair question to ask whether each of us picked up our original ball, or the other one. If you do the same thing with protons, the question has no meaning, because protons are indistinguishable. Likewise, asking whether the Oxygen atoms which make up the water are paired with the same protons, or different ones is equally meaningless. The Lego analogy is equally flawed, because Lego blocks are distinguishable and protons are not.
Any argument that the water is “different” because different protons are now paired with each Oxygen atom than before has no basis in physics.
There are limits, but drinking a liter of heavy water, for example, would have no noticable effect on a human. If you feed small mammals (which presumably are analogous to humans for this) heavy water, there is little effect until the hydrogen of the water in the body is roughly 20% D. At about 25% sterility results, and at about 30% death.
Most likely this is a result of differing rates of chemical reactions resulting from kinetic isotope effects. (Different masses result in different vibrational characteristics, which in turn means slightly different bond energies, so reactions which form or break such bonds will occur at different speeds.)
Some bacteria can live when fully deuterated. I guess mammals are just wimpy
I’m not entirely sure what you’re trying to say, ZenBeam. It’s entirely possible to track where each atom goes in biological reactions by performing radioactive trace experiments. The classic experiment for photosynthesis was to grow the single-celled alga Chlorella in H[sub]2[/sub][sup]18[/sup]O. Radioactive [sup]18[/sup]O[sub]2[/sub] was evolved after exposure to light, showing that oxygen is produced from water. Note that the water has to be broken down into its constituent atoms in order for this to happen.
In this experiment, you aren’t tracking each atom, you’re tracking [sup]18[/sup]O collectively. And yes, you can certainly distinguish between [sup]18[/sup]O and [sup]16[/sup]O.
If you were to take the [sup]18[/sup]O and use it to burn Hydrogen, to get water, there is no physical justification for saying something like “the water that results is different because it is made using different hydrogen atoms than the water you started with”*. Protons are all indistinguishable, so you can’t say they’re different.
(*)Not quoting anyone here, just trying to make the sentence easier to understand.
OK, ZenBeam, I kind of see your point. But allow me to play Devil’s Advocate for a bit.
Sure, but if you fed a plant a single molecule of H[sub]2[/sub][sup]18[/sup]O (not that we have the technology to do this) and you eventually got back a single molecule of [sup]16[/sup]O[sup]18[/sup]O, wouldn’t it be reasonable to say that the original water molecule was hydrolyzed via photosynthesis? Isn’t this the equivalent of (if not actually tracking) a single atom?
Again, you could tag the proton with a neutron to get deuterium. Feed it to a plant in the form of heavy water or whatever and wait for it to come back in a different molecule. Isn’t this in effect tracing the path of a single atom?
I’m not suggesting you can’t track the [sup]18[/sup]O and the [sup]16[/sup]O separately, but unless you’ve got 10[sup]30+[/sup] different isotopes available to uniquely tag each water molecule on Earth, I don’t see how that helps. I think if the water a billion years ago was made mostly using [sup]18[/sup]O and now it’s mostly [sup]16[/sup]O, everyone would agree it’s different water, but I haven’t seen any evidence of anything like that.
It’s tracing a single atom, but only if there isn’t any other Deuterium around. If one in a trillion Hydrogen atoms are Deuterium (I’m making that number up), and you leave your “tagged” proton in a mole of water for a billion years, how are you going to pick it out from the other 1.2 trillion deuterium atoms at the end?
