Deuterium purity check

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steve_rb
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Deuterium purity check

Post by steve_rb »

We have an old cylinder of D2 gass from a local supplier but I am not sure about its D2 purity. What is the simplest method for checking the purity? Someone was saying using GC and D2 at about minus 100 deg C (-100 DegC) it is possible to determine the H2/D2 ration up to two significant digit. Also I have seen a paper saying RGA (Residual Gas Analyzer) in high vacuum is useful. Anyone has any experience in this?
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Dennis P Brown
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Re: Deuterium purity check

Post by Dennis P Brown »

A residual gas analyser is the gold standard for testing gasses for trace contaminates - first, get a back ground trace with the RGA for your system (no deuterium added) and then just admit a very small amount of the "unknown" gas into your chamber/system and use the RGA to determine all trace gasses. There are companies that do this (send them a small sample of the gas) if you do not have access to an RGA. Not sure the cost is worth that effort compared to buying a new cylinder of deuterium.

No idea what GC stands for so I can't comment on that.
John Futter
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Re: Deuterium purity check

Post by John Futter »

Gas Chromatograph
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Dennis P Brown
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Re: Deuterium purity check

Post by Dennis P Brown »

Mr. Futter, thanks.

Wouldn't it be easier just to try the gas in a fusor? (assuming one has the proper power supply and vacuum.)
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Rich Feldman
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Re: Deuterium purity check

Post by Rich Feldman »

[edit] The following message is fusor-oriented, but OP is about D2 purity per se -- not necessarily for a fusor.[\edit]

Yes, what Dennis said. Let me elaborate.

If the cylinder label says Deuterium, and it's more than 10% "full", then it almost certainly contains deuterium.
Commercially pure deuterium is at least 99.7% D2, and the grades go up from there.
http://www.mathesongas.com/pdfs/product ... re-gas.pdf

Unless regular hydrogen has a strong poisoning effect on the intended D-D fusion,
I bet your fusion rate will be practically the same for 99.995%, 99.7%, or for that matter 90% D2.

Hmm.
In today's science fairs, a plain neutron-producing fusor belongs in the _engineering_ category.
To qualify as a _physics_ project, which implies scientific investigation, one could try to quantify the effect of deuterium purity.
Mixing D2 and H2 is the easy part, what with oil-filled test tube reservoirs and PEM electrolysis cells.
Getting a sufficiently stable and repeatable fusor plant is the hard part.

For general interest:
today's Internet search about D2 purity pointed out a benchtop apparatus for isotopic purification.
It happens to also be a "small world" example, since author Kuppermann once taught me chemistry.
http://authors.library.caltech.edu/12983/1/PERjpe74.pdf
All models are wrong; some models are useful. -- George Box
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Richard Hull
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Re: Deuterium purity check

Post by Richard Hull »

Purity of deuterium in a cylinder clearly marked deuterium is never an issue. It will work in a good fusor. The issue at question........Is your fusor good enough to have a mostly deuterium atmosphere in it when to let in the gas?

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
JohnCuthbert
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Re: Deuterium purity check

Post by JohnCuthbert »

Measuring the density is probably good enough to tell you if it's hydrogen, deuterium or air.
Of course, it won't help much with mixtures.
George Schmermund
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Re: Deuterium purity check

Post by George Schmermund »

My guess is that the deuterium has all decayed away by now. I recommend that you send me the cylinder so that it can be disposed of properly. I'll provide this service for free.
Anything obvious in high vacuum is probably wrong.
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Dennis P Brown
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Re: Deuterium purity check

Post by Dennis P Brown »

Mr. Schmermund, not everyone is knowledgeable and might not realize you are joking. You might want to add that it is tritium that has a short (twelve or so years) half life and not deuterium (which is stable but may have a half life of 10^35 years ...) just to help those without the background to catch the joke (which was rather funny ... most people here would like a free cylinder of deuterium, too ...)
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