# Heavy Water **URL:** \ **Category:** Factual Questions\ **Created:** [April 26, 2000, 6:03pm UTC](https://boards.straightdope.com/t/heavy-water/11189 "2000-04-26T18:03:00Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Wendy\_C.Brooks](https://avatars.discourse-cdn.com/v4/letter/w/cab0a1/32.png) [@Wendy\_C.Brooks](https://boards.straightdope.com/u/Wendy_C.Brooks)\ **Post date:** [April 27, 2000, 5:59am UTC](https://boards.straightdope.com/t/heavy-water/11189/1 "2000-04-27T05:59:00Z")
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 ---
**Author:** ![Andy](https://avatars.discourse-cdn.com/v4/letter/a/aeb1de/32.png) [@Andy](https://boards.straightdope.com/u/Andy)\ **Post date:** [April 26, 2000, 6:03pm UTC](https://boards.straightdope.com/t/heavy-water/11189/2 "2000-04-26T18:03:00Z")
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. ---
**Author:** ![Guy\_Propski](https://avatars.discourse-cdn.com/v4/letter/g/5e9695/32.png) [@Guy\_Propski](https://boards.straightdope.com/u/Guy_Propski)\ **Post date:** [April 26, 2000, 6:05pm UTC](https://boards.straightdope.com/t/heavy-water/11189/3 "2000-04-26T18:05:00Z")
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. ---
**Author:** ![system](https://global.discourse-cdn.com/straightdope/original/2X/e/e489c3b7d8fce19c4b355dd4fc3f88cc39c34b87.png) [@system](https://boards.straightdope.com/u/system)\ **Post date:** [April 26, 2000, 6:07pm UTC](https://boards.straightdope.com/t/heavy-water/11189/4 "2000-04-26T18:07:00Z")
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](http://vm.cfsan.fda.gov/~dms/cos-toc.html) * * * “Why, sometimes I’ve believed as many as six impossible things before breakfast!” - the White Queen ---
**Author:** ![Andy](https://avatars.discourse-cdn.com/v4/letter/a/aeb1de/32.png) [@Andy](https://boards.straightdope.com/u/Andy)\ **Post date:** [April 26, 2000, 6:26pm UTC](https://boards.straightdope.com/t/heavy-water/11189/5 "2000-04-26T18:26:00Z")
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? ---
**Author:** ![Guy\_Propski](https://avatars.discourse-cdn.com/v4/letter/g/5e9695/32.png) [@Guy\_Propski](https://boards.straightdope.com/u/Guy_Propski)\ **Post date:** [April 26, 2000, 6:37pm UTC](https://boards.straightdope.com/t/heavy-water/11189/6 "2000-04-26T18:37:00Z")
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… ---
**Author:** ![KarmaComa](https://avatars.discourse-cdn.com/v4/letter/k/e36b37/32.png) [@KarmaComa](https://boards.straightdope.com/u/KarmaComa)\ **Post date:** [April 26, 2000, 7:05pm UTC](https://boards.straightdope.com/t/heavy-water/11189/7 "2000-04-26T19:05:00Z")
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… ---
**Author:** ![Boris\_B](https://avatars.discourse-cdn.com/v4/letter/b/fbc32d/32.png) [@Boris\_B](https://boards.straightdope.com/u/Boris_B)\ **Post date:** [April 26, 2000, 7:15pm UTC](https://boards.straightdope.com/t/heavy-water/11189/8 "2000-04-26T19:15:00Z")
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. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [April 26, 2000, 8:36pm UTC](https://boards.straightdope.com/t/heavy-water/11189/9 "2000-04-26T20:36:00Z")
So does "regular heavy water’ have only deuterium or a mix of deuterium and hydrogen? * * * _It is too clear, and so it is hard to see._ ---
**Author:** ![KarmaComa](https://avatars.discourse-cdn.com/v4/letter/k/e36b37/32.png) [@KarmaComa](https://boards.straightdope.com/u/KarmaComa)\ **Post date:** [April 26, 2000, 9:04pm UTC](https://boards.straightdope.com/t/heavy-water/11189/10 "2000-04-26T21:04:00Z")
> [@](#): > > 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. ---
**Author:** ![douglips](https://avatars.discourse-cdn.com/v4/letter/d/e68b1a/32.png) [@douglips](https://boards.straightdope.com/u/douglips)\ **Post date:** [April 26, 2000, 9:38pm UTC](https://boards.straightdope.com/t/heavy-water/11189/11 "2000-04-26T21:38:00Z")
> [@](#): > > 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? ---
**Author:** ![KarmaComa](https://avatars.discourse-cdn.com/v4/letter/k/e36b37/32.png) [@KarmaComa](https://boards.straightdope.com/u/KarmaComa)\ **Post date:** [April 26, 2000, 9:49pm UTC](https://boards.straightdope.com/t/heavy-water/11189/12 "2000-04-26T21:49:00Z")
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! ---
**Author:** ![Andy](https://avatars.discourse-cdn.com/v4/letter/a/aeb1de/32.png) [@Andy](https://boards.straightdope.com/u/Andy)\ **Post date:** [April 26, 2000, 11:29pm UTC](https://boards.straightdope.com/t/heavy-water/11189/13 "2000-04-26T23:29:00Z")
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. ---
**Author:** ![Harmonious\_Discord](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@Harmonious\_Discord](https://boards.straightdope.com/u/Harmonious_Discord)\ **Post date:** [April 26, 2000, 11:41pm UTC](https://boards.straightdope.com/t/heavy-water/11189/14 "2000-04-26T23:41:00Z")
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. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [April 27, 2000, 1:35am UTC](https://boards.straightdope.com/t/heavy-water/11189/15 "2000-04-27T01:35:00Z")
Yes, there does exist HDO. That’s the way most deuterium in ordinary water is combined. * * * “Scissors Defeats Rock” – The Onion ---
**Author:** ![Andy](https://avatars.discourse-cdn.com/v4/letter/a/aeb1de/32.png) [@Andy](https://boards.straightdope.com/u/Andy)\ **Post date:** [April 27, 2000, 2:28am UTC](https://boards.straightdope.com/t/heavy-water/11189/16 "2000-04-27T02:28:00Z")
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. ---
**Author:** ![Sofa\_King](https://avatars.discourse-cdn.com/v4/letter/s/58956e/32.png) [@Sofa\_King](https://boards.straightdope.com/u/Sofa_King)\ **Post date:** [April 27, 2000, 3:00am UTC](https://boards.straightdope.com/t/heavy-water/11189/17 "2000-04-27T03:00:00Z")
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. ---
**Author:** ![Sofa\_King](https://avatars.discourse-cdn.com/v4/letter/s/58956e/32.png) [@Sofa\_King](https://boards.straightdope.com/u/Sofa_King)\ **Post date:** [April 27, 2000, 3:03am UTC](https://boards.straightdope.com/t/heavy-water/11189/18 "2000-04-27T03:03:00Z")
My above post seems to have emitted an “i” particle from “tritium.” ---
**Author:** ![bibliophage](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bibliophage/32/7615_2.png) [@bibliophage](https://boards.straightdope.com/u/bibliophage)\ **Post date:** [April 27, 2000, 4:02am UTC](https://boards.straightdope.com/t/heavy-water/11189/19 "2000-04-27T04:02:00Z")
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. Work is the curse of the drinking classes. (Oscar Wilde) ---
**Author:** ![Steve-o](https://avatars.discourse-cdn.com/v4/letter/s/ecc23a/32.png) [@Steve-o](https://boards.straightdope.com/u/Steve-o)\ **Post date:** [April 27, 2000, 4:42am UTC](https://boards.straightdope.com/t/heavy-water/11189/20 "2000-04-27T04:42:00Z")
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. [ballparking] In a first order reaction, the rate of reaction will be about 7 fold slower for the deuterium oxide. [/ballparking] 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] [Next page](https://boards.straightdope.com/t/heavy-water/11189.md?page=2)