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Author: Subject: Nitrogen Generator
JJay
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[*] posted on 19-12-2015 at 15:17
Nitrogen Generator


I was thinking about distilling some ether, and I don't think doing it in air is such a great idea, so I thought I would try doing it in a stream of nitrogen. I could use a nitrogen tank, but what about generating nitrogen using sulfamic acid and sodium nitrite solution? I could dry the nitrogen in MgSO4 or molecular sieves.... I believe that this sort of setup could be useful for other procedures that require inert gas.... Is there any major advantage to using a tank of gas instead?
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Etaoin Shrdlu
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[*] posted on 19-12-2015 at 15:28


Ammonium chloride and sodium nitrite, even cheaper.

EDIT: Yes, there's an advantage to a gas tank, no scrubbing and less expensive all told.

[Edited on 12-19-2015 by Etaoin Shrdlu]
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[*] posted on 19-12-2015 at 16:05


Distilling under nitrogen will help you just until your entire apparatus is filled with ether vapor. Then it won't make much of a difference over air. I'd just flame-dry the glassware and distill with a drying tube.



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JJay
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[*] posted on 19-12-2015 at 17:39


Quote: Originally posted by subsecret  
Distilling under nitrogen will help you just until your entire apparatus is filled with ether vapor. Then it won't make much of a difference over air. I'd just flame-dry the glassware and distill with a drying tube.


That's fine, but my concern is actually oxygen, not water vapor.
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JJay
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[*] posted on 19-12-2015 at 17:57


Quote: Originally posted by Etaoin Shrdlu  
Ammonium chloride and sodium nitrite, even cheaper.

EDIT: Yes, there's an advantage to a gas tank, no scrubbing and less expensive all told.

[Edited on 12-19-2015 by Etaoin Shrdlu]


Cool - I don't happen to have any ammonium chloride, but I'll keep that in mind.
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[*] posted on 19-12-2015 at 18:33


Just distill it in air; the boiling ether pushes out the air in the apparatus anyway, and unless you have a room full of nitrogen to distill it in there's essentially no difference when you add a generator. Do the distillation outside, in a fume hood, or a very well-ventilated room. Use a warm water or steam bath as opposed putting the boiling flask very close to any hot metal surface.



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JJay
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[*] posted on 20-12-2015 at 07:14


It does appear that it isn't absolutely essential to distill diethyl ether in inert gas, although it is sometimes recommended.
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[*] posted on 20-12-2015 at 09:50


If you distill under a stream of nitrogen, the ether volatility will result in the loss of the majority of your yield from the collection vessel.
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20-12-2015 at 13:35
JJay
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[*] posted on 20-12-2015 at 14:58


Quote: Originally posted by The_Davster  
If you distill under a stream of nitrogen, the ether volatility will result in the loss of the majority of your yield from the collection vessel.


I think it would depend on temperatures. Anyway, this thread isn't really about ether.I would definitely prefer to distill it in nitrogen if that is convenient, though.

Are there any good substitutes for sodium nitrite that are both cheap and easy to obtain?

[Edited on 20-12-2015 by JJay]
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BromicAcid
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[*] posted on 20-12-2015 at 18:48


Stream of nitrogen? You're missing some key aspects here of distillation. Look up a nitrogen bubbler. That will keep everything inerted (after initially inerting the setup) and will allow you to monitor the nitrogen flow. Producing the nitrogen in that way is an interesting way to approach it. Your drying agent all depends on how dry you want your ether in the end. Most home chemists don't have the technique or transfer capabilities to need it as dry as say magnesium perchlorate can get it.



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JJay
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[*] posted on 20-12-2015 at 19:09


I would probably prefer phosphorus pentoxide if I wanted things that dry. Also, I would probably use argon, but this discussion is about nitrogen.
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[*] posted on 20-12-2015 at 19:43


Sodium nitrite is fairly cheap and easy to obtain online as a food preservative. Check Amazon, you can buy 2 pounds for fairly cheap, around 15 dollars.
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JJay
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[*] posted on 20-12-2015 at 20:35


Quote: Originally posted by ParadoxChem126  
Sodium nitrite is fairly cheap and easy to obtain online as a food preservative. Check Amazon, you can buy 2 pounds for fairly cheap, around 15 dollars.


It seems like most reactions that generate nitrogen gas require expensive reagents that are only available through chemical suppliers or sodium nitrite.

I'm not sure that decomposing ammonia with bleach and bubbling the gas produced through sulfuric acid is such a great idea.
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[*] posted on 20-12-2015 at 23:33


Of course, for significant quantities of nitrogen, an air separation diffusion membrane is always an option, but small ones are difficult to source.
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[*] posted on 21-12-2015 at 00:42


Mellor vol. 8 in the ScienceMadness library lists a large number of reactions that create nitrogen. Most involve the use of an oxidizer on an ammonia salt, but one that caught my eye involves 200 mL 5% of sodium hypochlorite solution and 1.146 grams of ammonium sulfate. Apparently ammonium chloride can be used too.

Hypochlorite isn't cheap, but it is completely OTC, as are ammonium sulfate and ammonium chloride... I wonder what side products might be produced by this reaction.
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JJay
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[*] posted on 21-12-2015 at 00:56


Quote: Originally posted by ParadoxChem126  
Of course, for significant quantities of nitrogen, an air separation diffusion membrane is always an option, but small ones are difficult to source.


Possibly several chambers could be set up separated by pinholes and evacuated... then air could be allowed to quickly diffuse into the apparatus and the nitrogen enriched gas in the final chamber removed.

[Edited on 21-12-2015 by JJay]
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[*] posted on 21-12-2015 at 04:31


Quote: Originally posted by JJay  
[...]Hypochlorite isn't cheap, but it is completely OTC, as are ammonium sulfate and ammonium chloride... I wonder what side products might be produced by this reaction.

To my opinion it is not a pleasant means of making N2. Side products are NH2Cl (chloramine) and NH2NH2 (hydrazine). Both are very toxic and hydrazine is a known carcinogen. Both are soluble in ether and will contaminate your product.
If you really want to do this, bring up the pH, before mixing NH4Cl and NaOCl. Without added acid you may also make some NCl3, although I do not really expect such quantities that it may result in explosions.




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[*] posted on 21-12-2015 at 18:14


Quote: Originally posted by JJay  

Possibly several chambers could be set up separated by pinholes and evacuated... then air could be allowed to quickly diffuse into the apparatus and the nitrogen enriched gas in the final chamber removed.

[Edited on 21-12-2015 by JJay]


Most air separation diffusion membranes work on the molecular level, similar to molecular sieves. Pinholes would be too large to encourage the separation of air into its constituent components.

[Edited on 12-22-2015 by ParadoxChem126]
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JJay
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thumbdown.gif posted on 22-12-2015 at 02:16


Quote: Originally posted by ParadoxChem126  
Quote: Originally posted by JJay  

Possibly several chambers could be set up separated by pinholes and evacuated... then air could be allowed to quickly diffuse into the apparatus and the nitrogen enriched gas in the final chamber removed.

[Edited on 21-12-2015 by JJay]


Most air separation diffusion membranes work on the molecular level, similar to molecular sieves. Pinholes would be too large to encourage the separation of air into its constituent components.

[Edited on 12-22-2015 by ParadoxChem126]


False.
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[*] posted on 22-12-2015 at 10:49


Really? Can you provide an example of pinholes being used to separate air? Diffusion membranes work on a much smaller level.
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JJay
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[*] posted on 22-12-2015 at 20:31


Quote: Originally posted by ParadoxChem126  
Really? Can you provide an example of pinholes being used to separate air? Diffusion membranes work on a much smaller level.


Yeah, many Graham's Law problems in high school and undergraduate textbooks discuss using pinholes for purifying gases. I'm not saying it is the approach I would favor, but it's certainly possible.
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[*] posted on 22-12-2015 at 20:34


Quote: Originally posted by woelen  
Quote: Originally posted by JJay  
[...]Hypochlorite isn't cheap, but it is completely OTC, as are ammonium sulfate and ammonium chloride... I wonder what side products might be produced by this reaction.

To my opinion it is not a pleasant means of making N2. Side products are NH2Cl (chloramine) and NH2NH2 (hydrazine). Both are very toxic and hydrazine is a known carcinogen. Both are soluble in ether and will contaminate your product.
If you really want to do this, bring up the pH, before mixing NH4Cl and NaOCl. Without added acid you may also make some NCl3, although I do not really expect such quantities that it may result in explosions.


Sodium azide (and other azides) are said to be useful for producing highly pure nitrogen.
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[*] posted on 22-12-2015 at 21:19


Quote: Originally posted by JJay  


Yeah, many Graham's Law problems in high school and undergraduate textbooks discuss using pinholes for purifying gases. I'm not saying it is the approach I would favor, but it's certainly possible.


I suppose. Due to their similar molecular weights, nitrogen and oxygen would be rather ineffectively separated by simple diffusion. It seems the very low flow rates through pinholes would explain why this technique is not practical for reasonable amounts of air.
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[*] posted on 22-12-2015 at 21:23


Quote: Originally posted by ParadoxChem126  
Quote: Originally posted by JJay  


Yeah, many Graham's Law problems in high school and undergraduate textbooks discuss using pinholes for purifying gases. I'm not saying it is the approach I would favor, but it's certainly possible.


I suppose. Due to their similar molecular weights, nitrogen and oxygen would be rather ineffectively separated by simple diffusion. It seems the very low flow rates through pinholes would explain why this technique is not practical for reasonable amounts of air.


Whether it is practical or not really depends on how bad you need the nitrogen....
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[*] posted on 28-12-2015 at 12:15


Probably the cheapest way is to use iron + water. It will also react with the oxygen in the air and make Fe(OH)2. The left over gas will be mostly N2 and argon.
You can also heat some metal powder to react with the oxygen.




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