[theThinker (OP)]

How easy or difficult to get 1 gram of pure isotope of a common substance - say ¹H?

[evan_au]

1 gram of pure isotope of a common substance - say ¹H?

From a physics viewpoint, this is pretty easy - commercial gas suppliers will provide an isotope mixture for you. Or you can get ordinary water from the tap.

I saw the very slim tank of hydrogen that the LHC used in their search for the Higgs Boson. Apparently, this small tank (perhaps 2 feet high and 6 inches in diameter) contains a 6-month supply of protons for the LHC.

"Pure" is a very relative concept. Just how pure?

If you use a commercial gas supplier, they will probably include about 0.02% of Deuterium (heavy hydrogen isotope) - unless they have found it commercially viable to separate out the Deuterium to sell for heavy water or as tracers in MRI machines and biochemistry.
https://en.wikipedia.org/wiki/Isotopes_of_hydrogen

If you want isotopically pure hydrogen, it is worthwhile to plan for a mass spectrometer/isotope separator before your experiment - this is easy for the LHC, since the whole machine is basically one big mass spectrometer.

Other atoms are not so easy, because there are multiple common isotopes, and the mass ratio between the different isotopes is a lot smaller than Hydrogen/Deuterium.

From a chemistry viewpoint, atomic hydrogen is highly unstable, and you can't buy it commercially. You have to produce it yourself by turning it into a plasma, or by turning it into a water solution, which will release dissolved ions.

[theThinker (OP)]

Hello Evan,

You say LHC has 6 month's supply of proton, not just pure isotope of ¹H. It seems I need a multi million dollar Lab to get 1 gram of pure ¹H isotope, never mind it is H² molecules. 

[chiralSPO]

It is quite easy to get pure ³¹P. This is the only stable isotope of phosphorus, and the others have relatively short half lives (a few weeks). see here: https://en.wikipedia.org/wiki/Isotopes_of_phosphorus

As far as I know, radioactive phosphorus is produced synthetically, but even if there were traces of, say, ³²P, one would only need to wait 80 half lives (about 3 years) to be certain that there wasn't even a single atom of ³²P remaining (assuming a mole of P to start with)

Why 80 half lives? This is abundantly cautious. If one had a mole (6.02×10²³ atoms) of ³²P, then it would take 79 divisions by two to get to a single atom (2⁷⁹ = 6.04×10²³), and then one more for the last to disappear. Of course, if one starts with a mole of P, nearly all of it is ³¹P, so it wouldn't take nearly as long for it all to decay, but once one gets down to only a handful of radioactive atoms, the statistics no longer work out to guarantee that half lives are consistent (there is a constant probability of a single atom decaying, so when there are many, many atoms one can predict the rate of decay quite accurately, but there could be a single atom that hangs around significantly longer than expected, messing up the final decay rate.)

[Bored chemist]

If you buy pepto bismol or the local equivalent from the chemist's it's isotopically pure bismuth.
Like Phosphorus, there's only 1 stable isotope.
The same is true of gold, but I'm not sure that counts as "common".

[theThinker (OP)]

OK, those with one stable isotope is easy.

Say just ¹H with no deuterium; tritium may be untraceable.

[Bored chemist]

You can buy deuterium depleted water.
https://www.sigmaaldrich.com/catalog/product/aldrich/195294?lang=en&region=GB&gclid=EAIaIQobChMIqdfIn8Lg2wIVU5nVCh3EIwudEAAYASAAEgJgjfD_BwE

it's not cheap and it's still got about 1ppm of deuterium in it.

[evan_au]

Hmm... $30 for 10 grams of H₂O. But almost 9 grams of that is Oxygen.
You are left with just over 1 gram of Hydrogen, after you remove the 1ppm of Deuterium...

What do you need it for, anyway?

[theThinker (OP)]

Hmm... $30 for 10 grams of H₂O. But almost 9 grams of that is Oxygen.
You are left with just over 1 gram of Hydrogen, after you remove the 1ppm of Deuterium...

What do you need it for, anyway?

Hello Evan,

$30 per 10 grams is very, very cheap to people who run $$$ experiments! Most university departments can afford it.

Natural abundance of deuterium in hydrogen is 1.56 % (I think this figure is % by number of atoms).So 1ppm is 0.0001% which is zero for many situations.

[evan_au]

Natural abundance of deuterium in hydrogen is 1.56 %

No, it's 0.02%.

If that is measured by atoms, that makes it 0.04% by mass.

Do look at: https://en.wikipedia.org/wiki/Isotopes_of_hydrogen

If the natural abundance of Deuterium were 1.56%, it would not have cost so much to extract heavy water from seawater, and the Germans wouldn't have used the factory in Norway.
See: https://en.wikipedia.org/wiki/Norwegian_heavy_water_sabotage

[syhprum]

to extract u235 from normal uranium 238 costs an awful amount of money

[evan_au]

Natural abundance of deuterium in hydrogen is 1.56 %

It is thought that almost all deuterium in the universe today was created during the Big Bang - at a level of about 26 deuterium atoms per million of "normal" hydrogen.

The amount of deuterium has been decreasing ever since; Deuterium is preferentially burned in stars, so new deuterium is formed very slowly, and any deuterium present is turned into helium very quickly.

See: https://en.wikipedia.org/wiki/Deuterium
Interestingly, the concentration of deuterium in comet 67P/Churyumov-Gerasimenko is about three times that of earth water. So don't get your water from there!

[theThinker (OP)]

Natural abundance of deuterium in hydrogen is 1.56 %

No, it's 0.02%.

If that is measured by atoms, that makes it 0.04% by mass.

Do look at: https://en.wikipedia.org/wiki/Isotopes_of_hydrogen

If the natural abundance of Deuterium were 1.56%, it would not have cost so much to extract heavy water from seawater, and the Germans wouldn't have used the factory in Norway.
See: https://en.wikipedia.org/wiki/Norwegian_heavy_water_sabotage

Yes, I got the decimal wrong, it is 99.985% and 0.015% from another source.

I think I want to start a facility to produce deuterium and make money!