Sciencemadness Discussion Board - Possible urgent scenario regarding the ampuling of nitrogen oxides

Possible urgent scenario regarding the ampuling of nitrogen oxides

numos - 1-1-2016 at 14:40

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.

annaandherdad - 1-1-2016 at 14:58

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.

diddi - 1-1-2016 at 14:59

interested to see results. I am planning to ampoule some unusual gasses also as I have LN2 available.

numos - 1-1-2016 at 15:05

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?

numos - 1-1-2016 at 15:07

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.

diddi - 1-1-2016 at 16:06

yeh the storage is the issue

numos - 1-1-2016 at 16:24

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)
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