# how to measure heavy water concentration

regular tap water contains small % D2O , let say a distillation process remove small amount of H2O . how can one measure this change using tools available to average person.

• Could you supply a source for the percentage of heavy water in ordinary tap water? – DJohnM Aug 19 '15 at 18:25
• @DJohnM : en.wikipedia.org/wiki/Heavy_water – michael501 Aug 19 '15 at 19:49
• tools available to [the] average person? This proably is available to the average person-who-has-the-cash. perkinelmer.com/Catalog/Family/ID/… – Solomon Slow Aug 19 '15 at 20:22
• @jameslarge , how about light index , or adding a fish to the container? – michael501 Aug 19 '15 at 20:24
• I don't know about the refractive index of heavy water, but I seriously doubt that a fish will give you a useful quantitative measure. (That is what you asked for---how can one measure this change.) – Solomon Slow Aug 19 '15 at 20:37

Apart from $D_2O$ (heavy water), natural water also contains $HDO$ (semi-heavy water) and of course $H_2O$.

The physical properties of these substances do vary from one to another, as can be seen from this Wikipedia comparative table. For example, the melting point of $D_2O$ differs sufficiently from that of $HHO$ or $H_2O$ to be measurable by a hobbyist or amateur scientist.

The problem is that deuterium ($D$) has very low natural abundance: only 1 in 6420 hydrogen atoms is deuterium (in the world's oceans), according to Wikipedia.

At such low abundance of $D_2O$ and $HHO$ the influence of these substances on the bulk properties of tap water is beyond reasonable means of measurement by an "average person". And a single electrolysis has only a small effect on these low abundances.

The same is true on the effect such low abundances (and any small changes thereof) on biological systems, even though much higher concentrations of $D$ does have a strong negative effect on the metabolism of most animals (like fish).

• HHO semi-heavy ? – DJohnM Aug 19 '15 at 21:05
• perhaps DHO , or H-O-D – michael501 Aug 19 '15 at 21:07
• HDO of course, not HHO. A typo that's been corrected. Thank you for pointing it out. – Gert Aug 20 '15 at 18:23

In "ordinary" water, about 156 out of 1,000,000 hydrogen atoms are deuterium.

If you were to pick any instant in time, these atoms would be arranged in water molecules as follows:$$HHO---0.999688024$$ $$HDO---0.000311951$$ $$DDO---0.000000024$$ So only about 24 molecules of true heavy water exist in a billion molecules of ordinary water.

In addition, these hydrogen and deuterium atoms are rapidly exchanged in water. If you were to watch a particular one of the tiny number of $D_2O$ molecules, (don't ask me how) you would see the D atoms swapped out (and possibly back in again) very quickly.

I don't know any "kitchen-sink" method to detect the effect of removing a few of the super abundant H atoms...

• how about tritium ? is high concentration of DDO generates it ? or it naturally exists. – michael501 Aug 19 '15 at 21:15
• @michael501 Tritium decays fairly quickly (12.3 years half life), so in nature, there's essentially no Tritium to speak of in oceans or tap water. It's essentially a man made element, though stars might have tiny amounts of it, but the short half life keeps it from being present in nature. – userLTK Jun 12 '16 at 6:08