numos
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Possible urgent scenario regarding the ampuling of nitrogen oxides
So I have a fascination with ampuling things, especially things difficult to keep in vials at standard pressure, and I decided to take a break from
o-chem today and ampule some Nitrogen dioxide / Dinitrogen tetroxide.
I've done this before using Cu / HNO3 and ice water and collected some gas in an ampule, but this time I wanted some frozen Dinitogen Tetroxide. So I
used dry ice / Acetone bath. I also found a better method to make NO2 from Sodium nitrite and HNO3.
I was a little surprised to get a deep blue liquid which I found out is Dinitrogen trioxide.
"It forms upon mixing equal parts of nitric oxide and nitrogen dioxide and cooling the mixture below −21 °C" - Wikipedia
So the reaction between Sodium nitrite and Nitric acid forms both Nitrogen dioxide and Nitrogen monoxide. the problem with this is, when I close the
ampule the Nitrogen trioxide will convert back to NO2 / NO. NO2 is not a problem it has a low vapour pressure. I'm pretty sure NO's vapour pressure is
enough to burst the ampule.
I have it sitting in the dry ice bath now, and as long as I have dry ice to keep it cold it should be fine... but am I right to fear ampuling it, and
is there a way to save this scenario?
I'll post pics of the Dinitrogen trioxide later, it's very pretty.
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annaandherdad
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It is difficult to make NO2 without making NO, and my experience is that the NO dissolves readily in liquid NO2, that is, at temperatures well above
the boiling point of NO but below that of NO2. Of course it is not just dissolving in it, it is reacting to form N2O3, which gives the blue color.
But as you raise the temperature toward the boiling point of NO2, the NO comes off.
It is difficult to eliminate all the NO without mixing with oxygen in the gas phase and giving it time to react. You have to do this before you cool
it, if you want to get pure liquid NO2.
Any other SF Bay chemists?
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diddi
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interested to see results. I am planning to ampoule some unusual gasses also as I have LN2 available.
Beginning construction of periodic table display
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numos
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Quote: Originally posted by annaandherdad  | It is difficult to make NO2 without making NO, and my experience is that the NO dissolves readily in liquid NO2, that is, at temperatures well above
the boiling point of NO but below that of NO2. Of course it is not just dissolving in it, it is reacting to form N2O3, which gives the blue color.
But as you raise the temperature toward the boiling point of NO2, the NO comes off.
It is difficult to eliminate all the NO without mixing with oxygen in the gas phase and giving it time to react. You have to do this before you cool
it, if you want to get pure liquid NO2. |
I see, but I have done it before with ice water, I though it wouldn't be a problem because it's not cold enough to form N2O3, but if NO dissolves in
liquid NO2 then there should be some NO present in that ampule... So at pressure (like 0.9-1.2atm), the NO2 will stay as a liquid and NO will stay
safely dissolved in it?
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numos
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| Quote: Originally posted by diddi | | interested to see results. I am planning to ampoule some unusual gasses also as I have LN2 available. |
Have done chlorine and ammonia already. Just haven't found a way to store them. 
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diddi
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yeh the storage is the issue
Beginning construction of periodic table display
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numos
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Solution and video. So I ended up taking the ampule out of the dry ice bath and placed it into ice water at 5oC. As it heated up NO was released and
NO2 came out the top of the ampule. After a while there was a aqua colored liquid left. (as opposed to royal blue)
I ampuled this and let it warm up in a brick box, and it seemed to work!
 
Attachment: NOx.mp4 (4.6MB)
This file has been downloaded 623 times
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