Deuterium Amount

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Rich Feldman
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Re: Deuterium Amount

Post by Rich Feldman » Mon Feb 10, 2014 12:21 am

Hi Aidan. Thank you for sticking with the unsolicited lesson.
You got 4 a, b, and c right this time.
But your final answer, the associated volume of D2 gas, is still wrong by a factor of more than 100.

In real life it's numerical answers that matter.
Please give it one more try, and perhaps show your work.

Beware of mixing up units, such as grams and kilograms.

* mass of deuterium in 1 liter of liquid D2O.
* mass of deuterium in 1 liter of gaseous D2.
* ratio of the two previous answers. Do you see how that's the same as the volume ratio
between portions of the two substances containing the same mass of deuterium element?
Express the result either way: amount of D2O consumed to make 1 liter of D2 gas,
or amount of D2 gas that could be evolved from 1 liter of D2O liquid.

-Rich
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Re: Deuterium Amount

Post by charlie_mccartney » Mon Feb 10, 2014 12:29 pm

All of this is covered in high school chemistry, it is just a matter of explaining the proper way to convert these units.
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Richard Hull
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Re: Deuterium Amount

Post by Richard Hull » Mon Feb 10, 2014 4:01 pm

A mole of heavy water is only 20 grams, ~ 20cc. If fully electrolyized that would make ~44 liters of D2 gas.

The last time I checked 100 cc of heavy water was about $65.00. If fully electrolyized, that's about 220 liters of D2 gas. The cost of that much bottled D2 would be well over $1000.00.

Still, electrolyizing is a process filled with purity issues when it comes to putting the gas into the chamber, but it can definitely be made to work.

Were I to do it. I would have the D2 gas go through dryerite first and finally through a 10 foot coil of copper tubing under LN2 before admitting it.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Rich Feldman
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Re: Deuterium Amount

Post by Rich Feldman » Wed Feb 12, 2014 11:01 pm

Oops, Richard, you had two values wrong, one by a factor of two.
Here with corrections:
A mole of heavy water is only 20 grams, ~ 18cc. If fully electrolyzed that would make 1 mole = 22.4 liters of D2 gas at STP.
Perhaps your analysis was remembered from long ago, and overlooked the diatomic nature of hydrogen gases.
100 grams of heavy water (only 90 ml, that's why it's called heavy)
would yield about 110 liters of deuterium gas.

That's consistent with the volume ratio I was leading Aidan to, using looked-up densities instead of having to learn about moles.
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Re: Deuterium Amount

Post by Richard Hull » Fri Feb 14, 2014 4:28 pm

Thanks for the correction. that's the kind of normal mistake I make when playing chemistry. I forgot about the mass of the neutron in the D....and with me loving neutrons...Go figure.

I think the upshot for both of us, in this thread, is to show any would-be "roll your own D2" person that there is a heck of a lot of D2 gas at STP in 100CC of fully electrolyized heavy water.

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
Retired now...Doing only what I want and not what I should...every day is a saturday.

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