Heavy Water

[Andy]

It's certainly as safe as common water and not radioactive. I can't for the life of me, however, see how this is anything other than a gimmick. Chemically, heavy water and 'normal' water are almost indistinguishable.

[Guy Propski]

The only difference between heavy water and regular water is that heavy water contains Hydrogen-2, a normal atom of hydrogren with the addition of one neutron. It's not radioactive.

Here's the FDA's "Cosmetics" page--you can look and see if "heavy water" is mentioned.

http://vm.cfsan.fda.gov/~dms/cos-toc.html

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"Why, sometimes I've believed as many as six impossible things before breakfast!" - the White Queen

[Andy]

There are differences between heavy water and normal water. But does the fact that deutero water (bp 101.4) boils at a slightly higher temperature than normal water mean it's better in cosmetic products?

[Guy Propski]

You're right, android, there are differences. But they are so small as to be unnoticable in everyday situations. Unless the poster is planning on using this face cream in a fusion reactor experiment...

[KarmaComa]

The reason that people have this misconception about heavy water being radioactive is that it is used as a coolant for nuclear reactors, etc. It's like sticking a hot iron in water. The water is ok, but you should still avoid sticking hot irons in your mouth. An addition to this senseless comparison is the fact that the water could burn you afterwards, and you sure as hell wouldn't want to put contaminated D2O on your face. It sounds cool, though... deuterium... heavy water... isotope...

[Boris B]

I think the other reason people have this misconception is, a water molecule can theoretically include one or two tritium atoms. This would be "extra-heavy water"; tritium is the two-neutron isotope of hydrogen, and it is radioactive.

Previous posts are right that deuterium and "regular heavy water" are not radioactive.

[ZenBeam]

So does "regular heavy water' have only deuterium or a mix of deuterium and hydrogen?

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It is too clear, and so it is hard to see.

[KarmaComa]

Originally posted by ZenBeam:
So does "regular heavy water' have only deuterium or a mix of deuterium and hydrogen?
Regular heavy water is D2O, using deuterium instead of hydrogen. Of course, dilute heavy water would be a mix of H2O and D2O, but I don't think there is such a thing as HDO, just because of the ionic bonding properties of water.

[douglips]

Regular heavy water is D2O, using deuterium instead of hydrogen. Of course, dilute heavy water would be a mix of H2O and D2O, but I don't think there is such a thing as HDO, just because of the ionic bonding properties of water.
??
How is an H ion different chemically from a D ion, and why would that difference mean you couldn't have HDO?

[KarmaComa]

Actually in hindsight that does sound kind of stupid. But maybe the extra mass of the D has something to do with it. I actually hate chemistry... now i've become kind of curious. Anyone know if DHO will form? I suppose the right person to ask would be someone who actually knows how heavy water is made in the first place!

[Andy]

Heavy water is simply produced by electrolysis of regular water. As the O-H bond is weaker (slightly) than the O-D bond (lower zero point energy, don't ask, I probably couldn't answer), O-H bonds are cleaved preferentially and so H2 is produced in preference to D2. Hence the water becomes enriched in D(2O). As for the H2O/DHO/D2O, i'm still thinking about that one.

[Harmonious Discord]

Side note on radioactivity.

04/26/86
The USSR reported the Chernobyl nuclear accident to the world. Nearby countries were reporting higher than normal radioactivity readings.

[dtilque]

Yes, there does exist HDO. That's the way most deuterium in ordinary water is combined.

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"Scissors Defeats Rock"
-- The Onion

[Andy]

That was my immediate thought too, HDO being the major non-H2O component of typical water. But then I got to thinking of the relative stability of D2O vs HDO and the facility of the 'hydrogen' exchange process and imagined that with D2O being thermodynamically more stable, all the dueterons may accrue as D2O rather than sitting around as HDO. I'll find the answer tomorrow when I consult god, aka Peter Atkins.

[Sofa King]

Deuterium (1p, 1n) is considered a "stable isotope" of hydrogen, although I had a chemistry teacher who insisted that it was radioactive, just with an exceedingly long half-life.

Tritium (1p, 2n), on the other hand, is fairly radioactive, can also be a component of heavy water, and has a half-life of approximately twelve years, according to this (http://www.internal.eawag.ch/~aeschbach/trhe3/constants.html#halflife).

I find it hard to believe that tritum could find its way into any commercially available product, as it is comparatively short-lived and difficult to find in nature.

[Sofa King]

My above post seems to have emitted an "i" particle from "tritium."

[bibliophage]

Heavy water most often refers to D2O. As far as I know, there’s no reason HDO should be less stable than H2O or D2O. I strongly suspect heavy water in nature is mostly HDO. I had an older physics professor who was always careful to call D2O "Double-heavy water" to distinguish it from HDO. Technically, any kind of water heavier than H2O can be called heavy water, including water made from tritium or from Oxygen-18.

By the way, I remember reading somewhere that heavy water can’t be used by the body, but I could never understand why not. I’m not sure if it’s true.


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Work is the curse of the drinking classes. (Oscar Wilde)

[Steve-o]

How much did that stuff cost? Deuterium oxide (D2O) is expensive. The cheapest I could find it (even in large quantities) was for a little over 40 cents per gram. Let’s assume that it does have benefits over water (which I seriously doubt) for the sake of argument. Wouldn’t it be cheaper to use a little more of the same stuff made with H20 water? Last month, my water bill cost me about half a cent per gallon. Translated, that's $ 0.0000013 per gram. Look back up at that $ 0.4 per gram of deuterated water. Or, you can look at it as $ 1514 per gallon of deuterated water.

All of the commercially available sources list the formula as "D2O", but I would imagine that in nature, you would mostly find DHO. As a funny side note (well, it's funny to me at least), the bottle label on the commercially available stuff tells you that deuterium oxide is hygroscopic. That is... it will absorb water from the atmosphere. Oooooo... wouldn't want my water to get wet (yeah, yeah... I know... dilution and all that. Just thought it was kinda funny man. Chill! Damn, man! Will you lay off already?!? Sheesh.).

Back to the OP, and to answer bibliophage's question about why the body can't use heavy water (it can, just not very successfully). The product is most likely safe to use. Water and deuterium oxide are almost identical in their physical properties, and will participate in the same chemical reactions, but... the kinetics of those reactions are not similar at all. In a first order reaction, the rate of reaction will be about 7 fold slower for the deuterium oxide. This can have some bad effects on biological systems, so I wouldn't recomend drinking concentrated batches of the stuff on a regular basis (although the small concentrations in a lotion (applied topically) would most likely be harmless, as we are exposed to small quantities of the stuff on a daily basis). A friend who I talked with about this told me about a study that he read once about a "deuterated dog". That is... the researchers wanted to see what would happen to the dog if heavy water were incorporated into its system. [long story ---> short] They gave the dog concentrated deuterated water to drink. The dog died. [/long story ---> short]

[bibliophage]

Natural heavy water apparently is mostly HDO, as I suspected. Isotopic Composition of Water (http://ucsu.colorado.edu/~jamisons/class/Chap2/observ.htm) gives the HDO proportion of sea water as 320 ppm. Since deuterium makes up roughly 150 per million of hydrogen atoms, there wouldn’t be much left over to make D2O. If the isotopes of hydrogen react at random with oxygen, we would expect that by chance only about 25 in one billion water molecules would be D2O.

By the way, the type of heavy water made with O-18 is 6 or 7 times more common than HDO.


The site BIOTECHNOLOGICAL POTENTIAL OF HEAVY WATER AND DEUTERATED COMPOUNDS (http://www.nbiap.vt.edu/brarg/brasym96/kushner96.htm) says
The widespread use of heavy water in clinical studies and treatments without reported adverse effects implies that it is not very toxic to humans. This is also suggested by animal experiments, in which toxic effects did not begin to appear until the D content of blood and body fluids and tissues was over 20% (Katz, 1960; 1965; Thomson, 1963). To attain such a concentration and adult human weighing about 70 kg would have to drink rapidly more than 10 L D2O.
The site also says C-D (carbon-deuterium) bonds are much stronger than C-H bonds, which surprised me. Also amphetamines "are more readily transported into the brain in the deuterated form."





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Work is the curse of the drinking classes. (Oscar Wilde)

[Wendy C. Brooks]

I recently received a skin moisturizer from my facialist. I note that it contains heavy water (ie D2O) which the label says is able to hydrate my skin better than regular water. The stuff is very refreshing and has a nice scent but I am concerned about the safety of spraying my face w/heavy water. Is this stuff radioactive or anything? And if it is safe to use, is there any reason to think it is good for my skin?

Thanks for any info,
AltheaVet

[Andy]

Aldrich supply 99% D20 at $51-50 for 100g, so it's not that expensive. And the fact that D2O is hygroscopic is a big problem in NMR spectroscopy.

[Andy]

Originally posted by Steve-o:
In a first order reaction, the rate of reaction will be about 7 fold slower for the deuterium oxide

This ballpark figure is pretty accurate! if anyone's interested, the term used here is kinetic isotope effect and involves the different rate at which molecules react (as a ratio) when the important site has either X-H or X-D (or even X-T). Commonly, the 'H' rates are observed between 1 and 7 times the rate of the 'D' molecule. The highest observed was k(H)/k(D) = 24, but this was probably due to tunnelling. k(H)/k(T) = 79 for the same reaction.

[C K Dexter Haven]

Here all along I thought it was from the famous quote, "He's not heavy, he's my water."

[KarmaComa]

Originally posted by bibliophage:
The site also says C-D (carbon-deuterium) bonds are much stronger than C-H bonds, which surprised me. Also amphetamines "are more readily transported into the brain in the deuterated form."So could deuterium get you high, even on an IV drip?

[Steve-o]

Originally posted by android209:
Aldrich supply 99% D20 at $51-50 for 100g, so it's not that expensive. And the fact that D2O is hygroscopic is a big problem in NMR spectroscopy.

Hey, thanks for the info post adjacent to the one I quoted. Sorry to nit-pick but, by my calculations $50 / 100g = $0.50 per gram. That’s 10 cents higher than the price I quoted of 40 cents per gram (actually 1kg for $424.50 also in Aldrich). By chemical standards, that’s not very expensive, but let’s look at what that would do to the price of a bottle of lotion. I looked at several bottles of lotion here at work, and the average had about 15 ingredients, and all of them had water listed as the primary ingredient. Let’s assume a 16 oz bottle of lotion with the lotion’s density being that of water (1g/mL). Let’s also assume that the D20 makes up 10% of the lotion.

10% of 16 oz (454g) = 45.4g

45g @ $0.40/g = $18

Basically, we’ve just added the whole $18 to the cost of the lotion because, had we used H2O, the cost of the water would have been pennies.