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Author: Subject: condensation of NO2
Natures Natrium
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[*] posted on 1-7-2005 at 17:48
condensation of NO2


Just a quick request for anyone who has ever managed to succeed at condensing NO2 to post info about it. I am having a heck of a time. Even though the Merck states that NO2 is a liquid at 21.15C, The NO2 in my recieving flask (which is submerged in an ice/salt bath, -5C) is staying the same toxic brown gas it usually is. I dont really have a way to pressurize the system safely, or I would try that to condense the gas and then bring it back to atmospheric pressure.

Any ideas?

Thanks,
Nature's Natrium

PS Oh no, don't tell me this is another "bromine-like" gas! :o:P

EDIT: Update, ok, after an hour I got maybe 2-3mL. :( This obviously isnt going to work the way I thought it would.

EDIT 2: Alright, so I ran some sulfur dioxide through the system, and upon contact with any brown gas it immeadiatly reduced it to colorless NO, and deposited a white solid all over the glassware. In particular the little pool of NO2 in the recieving flask looks to have turned into a nice little chuck of SO3. :D

I need to find some way to mix dry air, NOx, and SO2 simultaneously. I will report back when I have more.;)

EDIT3: I alternated SO2 and NO2 and air for a bit, pasting the inside of the glassware with a frosting of what should be SO3. I vented the system via water aspirator, dissassembled it, capped one end of the condenser with a ground glass stopper, and washed it out with 83% (used to be 98%, half opened bottle of ACS) sulfuric acid. I used about 20 mL, then dumped this into recieving flask (washing the vacuum adapter in the process), where the rest of the solid was absorbed. The unfortunate thing is that there must have been some NOx beneath the cake formed in the bottom of the recieving flask, as the sulfuric acid is distinctly yellow. :( This is unfortunate because it likely now has dissolved NOx/ nitrosylsulfuric acid in it, rendering a density measurement useless. I dont know how I can 'prove' I have SO3 now, since it was probably all used up in the 17% water my sulfuric acid contains. Bummer. :mad:

[Edited on 2-7-2005 by Natures Natrium]

[Edited on 2-7-2005 by Natures Natrium]

[Edited on 2-7-2005 by Natures Natrium]




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[*] posted on 1-7-2005 at 19:47


I believe that I made NO2 once by distilling a mixture of concentrated H2SO4 with NaNO3 with no regard for temperature or pressure. I ended up with a deep brown/black/red liquid that was highly mobile that I took for fuming nitric acid however at a later date I found that leaving a few milliliters in the open caused them to volitize away completely rapidly, it was shortly after this that I found I may have condensed NO2 instead of the expected nitric acid. It condensed in the leibig using ice water running through it.



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Natures Natrium
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[*] posted on 1-7-2005 at 20:20


Hmm, well, I'm not sure what the deal is then. I was using a 300mm west condenser with ice water in it, and the recieving flask submerged in an ice/salt bath like I said. Perhaps because the NO2 was dried (over CaCl2) it refused to condense?

More experimentation will tell. My immeadiate goal here is to absorb SO3 into sulfuric to make 60% oleum, which is useful for a number of things.

How to make that damn NO2 condense in an anhydrous enviroment at atmospheric pressure? I really dont want to (can't) blow $20 on dry ice evey time I need to condense a troublesome poisonous gas. :(

Thoughts, anyone?




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[*] posted on 1-7-2005 at 20:36


I read somewhere that NO<sub>2</sub> forms an equilibrium with N<sub>2</sub>O<sub>4</sub> and that cooling NO<sub>2</sub> pushes it towards N<sub>2</sub>O<sub>4</sub>. By liquifying NO<sub>2</sub> you should be able to get fairly pure N<sub>2</sub>O<sub>4</sub>.

I found this but its not very clear about it:
http://en.wikipedia.org/wiki/Dinitrogen_tetroxide

[Edited on 7/2/2005 by Scratch-]
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