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Author: Subject: Purifying Deuterium Chloride solution
sbreheny
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[*] posted on 2-8-2014 at 17:45
Purifying Deuterium Chloride solution


Hi all,

I recently purchased on eBay 50g of 32% deuterated hydrochloric acid in D2O. I was really looking for a sample of D2O but I figured that this was even better since I could always neutralize it and separate out the D2O if I needed. Unfortunately, when it arrived, I found that the bottle had been sealed inside a shipping container for many years and had eaten through its own cap during that time, so that the acid is contaminated by dissolved organics from the plastic. It was still contained within the plastic bag which surrounded the bottle, so that I recovered almost the entire original volume in a new glass container.

I am looking for suggestions which would allow me to purify this to remove the brown dissolved contaminants. Ideally, I'd like to get something as close to the original 32% deuterium chloride in D2O as I can. However, I am also open to options which result in fairly pure D2O. I guess my highest priority is to get as little remaining protium (Hydrogen 1) contamination as possible. I realize that this is challenging because no doubt there is hydrogen in the contaminants and some of that must have dissociated in the heavy water/acid.

Ideas?

Thanks,
Sean
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Metacelsus
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[*] posted on 2-8-2014 at 19:13


My idea: Get a refund.

Removing protium contamination from heavy water is probably not worth the effort.

[Edited on 3-8-2014 by Cheddite Cheese]




As below, so above.

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[*] posted on 2-8-2014 at 19:21


I second that idea.



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sbreheny
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[*] posted on 2-8-2014 at 21:10


OK, yes, if I needed this for some special purpose, then yes, I agree. However, I have not seen heavy water available to hobbyists in a long time, and I don't think this guy has more of this, so if I get a refund and have to send it back, I am in a worse situation than I am now. Even if all of the hydrogen from the organic material were to be incorporated into the water, it would still be probably >90% heavy water, and that's a whole lot better than nothing.
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sbreheny
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[*] posted on 2-8-2014 at 21:12


Let me clarify something - I do not expect to separate out any protium which has already been incorporated as H3O+ ions, H2O, or HCL. I just would prefer to use some kind of reaction to purify it which would not create additional amounts of these species in the process. Right now, it is colored dark brown and I just want to get most of that junk out of it!

[Edited on 3-8-2014 by sbreheny]
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Zyklon-A
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[*] posted on 2-8-2014 at 21:40


If you knew what the destroyed cap was made out of that would be a start.
Distillation should give the results you want either way.




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prof_genius
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[*] posted on 3-8-2014 at 00:54


Try distilling it under a dry inert atmosphere.
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[*] posted on 3-8-2014 at 01:40


Distilling 32 % DCl won't work very well.

The DCl gas would come off until you reached the azeotrope - about 20% (I'm guessing it's about the same as the HCl H2O azeotrope which is 20.2% HCl).
If you trapped that gas somehow and then dissolved it back in the distilled acid you would get back to (nearly) what you started.

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[*] posted on 3-8-2014 at 07:18


How about neutalizing the DCl with sodium carbonate and then distilling the D2O?



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[*] posted on 4-8-2014 at 03:19


How would freezing work?
HCl*3H2O (about 40 % HCl) freezes at -25 celsius. It should be frozen out of the 32 % DCl till an eutectic with HCl*6H2O is reached at -73 celsius and about 26...27 % DCl.
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[*] posted on 4-8-2014 at 06:03


D2O not available to hobbyists in a long time? Have you looked here?



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[*] posted on 4-8-2014 at 15:53


Quote: Originally posted by sbreheny  
OK, yes, if I needed this for some special purpose, then yes, I agree. However, I have not seen heavy water available to hobbyists in a long time, and I don't think this guy has more of this, so if I get a refund and have to send it back, I am in a worse situation than I am now. Even if all of the hydrogen from the organic material were to be incorporated into the water, it would still be probably >90% heavy water, and that's a whole lot better than nothing.


Not true. United Nuclear has sold D2O in small amounts for years. I have 120 gm of it, two 10 gm and a 100 gm bottle. From the very link APO provided.




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sbreheny
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[*] posted on 5-8-2014 at 17:09


I actually found that link a few hours after I posted here saying that I had not seen it in a while. I usually look for chemicals on eBay and Amazon and I've never seen it come up in searches there until I saw the one I bought. I am surprised that I didn't come across the United Nuclear offering before because I have ordered other things from them. Thanks for the link.

I would still like to try purifying mine and I think I may resort to neutralizing with a non-hydrogen-containing base (like Sodium Carbonate as someone suggested) and then distilling to get just D2O.

Quote: Originally posted by APO  
D2O not available to hobbyists in a long time? Have you looked here?
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[*] posted on 8-8-2014 at 03:38


Try activated charcoal (dried).
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[*] posted on 11-8-2014 at 05:25


Stratetgy: Separate out the H2 and D2 as gases. This should reduce the presence of impurities and a cooling of the gas mixture, given the relative weights of the gases, could improve the D2 concentration as well.

Try adding Zn, boil and collect the gases. Cool to separate out any hydrocarbons, or captured distilled D2O and H2O, which you can recycle.

From the DCl, you get D2 and ZnCl2.

From the boiled H2O and D2O with Zn, you get Zn(OH)2, Zn(OD)2, H2 and D2.

As Zn(OH)2 (also I would guess the Zn(OD)2 as well) decompose releasing its water at 125 C, apply mild heat to the dry salt, to retrieve any D2O along with H2O to recycle.

[Edited on 12-8-2014 by AJKOER]
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sbreheny
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[*] posted on 4-9-2014 at 22:15


I finally got a chance to do more work on this and I managed to purify it by distillation. I just distilled it directly without neutralizing the acid, using a fume hood.

The mass of the starting material was 39.92g. The mass of the product was 31.98g. This seems to be an excellent yield given that there was a visible amount of contaminant solid remaining in the boiling flask and a large amount of DCl was lost as gas (assuming that the azeotrope is the same mass percent for DCl in D2O as HCl in H2O, then the product should be about 20% DCl by mass, but the original label stated 35% DCl by mass - although some was probably lost in reaction with the plastic that it ate).

The starting material was a dark brown opaque liquid with a horrible foul smell (not just the normal fuming HCl smell). The product has almost no smell (lower DCl concentration so much less DCl outgassing) and is clear. pH test paper shows that its pH is 1 or less (as low as the paper goes). Density of the product is (very roughly) 1.3g/mL. My back of the envelope calcs suggest that it should be 1.2g/mL. When I measured 1.3, I was only estimating volume by the graduations on a bottle, I did not yet do a proper volume measurement.

One remaining question is how much D vs H exchange happened due to mixing with water vapor in the air during the distillation. If it absorbed H2O from the air, that could falsely "improved" my yield.

Thanks for your help,

Sean
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[*] posted on 5-9-2014 at 05:03
Measuring Iostopic Composition


Probably the easiest method of measuring the actual isotopic composition is with a refractometer.

See Section 1-2.16 in:
http://books.google.com/books?id=HwhTSGufJdYC&pg=PA26&am...

But you need a good refractometer to be very useful.

The refractive index difference is 0.004687, and is linear with D molar concentration, so a cheap refractometer reading to 0.001 will only give you a rough estimate that can distinguish between 0%, 20%, 40%, etc. but not finer than that. A common type used for sugar content (measuring in Brix from 0-10% Brix) can read to 0.1% Brix, which corresponds to an RI resolution of 0.00014 and an isotope concentration resolution of about 3%.
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sbreheny
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[*] posted on 5-9-2014 at 18:11


Quote: Originally posted by careysub  
Probably the easiest method of measuring the actual isotopic composition is with a refractometer.

See Section 1-2.16 in:
http://books.google.com/books?id=HwhTSGufJdYC&pg=PA26&am...

But you need a good refractometer to be very useful.

The refractive index difference is 0.004687, and is linear with D molar concentration, so a cheap refractometer reading to 0.001 will only give you a rough estimate that can distinguish between 0%, 20%, 40%, etc. but not finer than that. A common type used for sugar content (measuring in Brix from 0-10% Brix) can read to 0.1% Brix, which corresponds to an RI resolution of 0.00014 and an isotope concentration resolution of about 3%.


Thanks for the suggestion - I don't have a refractometer and I don't think I am going to buy one just for this investigation.
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[*] posted on 5-9-2014 at 18:16


I obtained a better density measurement using a volumetric flask: 1.184g/mL. Alfa Aesar's online catalog lists the density of 20% w/w DCl in D2O as 1.20g/mL with a boiling point of 108 deg C. I observed 108 deg C during most of the time that the product was coming over during the distillation. I'm pretty happy with that result.

[Edited on 6-9-2014 by sbreheny]
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[*] posted on 5-9-2014 at 18:44


I wanted to share a few photos of my distillation set-up for doing this. One photo shows the "before and after" shot of the contaminated DCl in D2O and the product. Neither of them is in the original bottle, which leaked, but the original label is on the "before" photo. The other two photos are the distillation set-up and a wider shot of it in my hood. I am in the process of converting an enclosed porch into a home lab and this is the centerpiece of it. The boiling flask is in a mineral oil bath and I used an aquarium circulation pump to cycle cool water through the condenser. When I took the photo, no product had come over yet - when it began to transfer, I added ice to the water container.

before and after smaller.jpg - 226kB distillation.jpg - 325kB hood.jpg - 362kB

[Edited on 6-9-2014 by sbreheny]
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[*] posted on 5-9-2014 at 20:22
Deuterium Element Display


A little off-topic perhaps - but a neat display in an element collection would be two test tubes, one with light water, and one with heavy side-by-side with something of a density between the two in both - floating in heavy water and sunk in light water.

There aren't two many cases where you can conveniently display two pure samples of different isotopes of an element.

Question: any suggestions for what would make a good float? You could always manufacture a float, but it is not a good demo because they could have been made differently. The same homogeneous substance in both is more compelling. Obviously insolubility is a requirement. Polystyrene has a density of 1.05 and would fit the bill.
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[*] posted on 5-9-2014 at 20:45


Or try putting normal water and heavy water in equal volumes on different sides of a balance. More difficult, and I like the polystyrene suggestion better.



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