Distilling HNO3 and fire hazards

[Trinitrotoluene]

I can recall the first time I tried to distill HON3 I lack proper equipment. But I decided to made some anyways. Well my nitric acid still I built was, 2 flask one 250ml and the other 125ml and I placed 92ml of concentrated H2SO4 in the 250ml one and added 150grams of NaNO3.After that I made my own stoppers out of Aluminium foil and used masking tape as a seal. Then as most people stated they use glass tubing but instead I don't have it so I used some clear PVC tubing that I stole from the local hospital,connected the 125ml flask with the Al foil stoppers, seal with masking tape,and started distilling. I'm not sure about the time but I can see that my tubing was under attack by the acid but I continued on distilling. After I made 10ml the point where the tubing connects the 250ml flask along with the Al foil stoppers started to melt, then bubble, as theres it started leaking HNO3 and NO2 gas I realized I was in trouble I turned off the hotplate and disconnected the tube leading to my 125ml flask,backed away,but right when backed away the tower of HNO3 and NO2 fumes ignited into a tower of intense flames. The fire was quite intense because HNO3 is a powerful oxidizer.As the fire burned I sent up a pretty good cloud of black smoke that smell corrosive. After I think 10 more seconds the fire died down but was still burning I poured some water on it to put it out. I had some clean up to do. But I got off pretty lucky because had I was distilling HNO3 indoors, it would had been a differnt problem as my house would had burned down. I was thinkng about doing indoors but decided outside so lucky. But after that I changed tubing as now my tubing is pure aluminium.Then I distilled the rest of my stff and got 30ml of red HON3.But I had learned from my mastakes.

[Zach]

I stand corrected on the aluminum reaction.

<small>[ January 28, 2003, 08:42 PM: Message edited by: Zach ]</small>

[knowledgehungry]

It might not have been the HNO₃ that reacted with the Al foil but rather the products of the HNO3 and PVC reaction. HNO3 will not usually react too badly with HNO3 however HCl and Al react pretty strongly and i believe that HCl is formed from the reaction of HNO3 and PVC.

<small>[ January 28, 2003, 06:33 PM: Message edited by: knowledgehungry ]</small>

[blindreeper]

I know this is old, but doesn't HNO3 react with Al?
I made a solar still type thing for nitric acid and after half an our the Al was eaten away, maybe cause Al foil is not pure?

[Arthis]

Normally, pure Al would be oxydised by HNO3 and form a small layer that stop corrosion (passivation). But any impurity is going to allow the oxydation to dig further inside the metal.

And normally passivation only happens with concentrated acid (I think). Maybe the layer is taken away because of the water ?

[Desmikes]

I’ve never tried to distill any nitric acid b/c from what I’ve read it is kinda troublesome and the yield is not all that great. So I don’t know much about properties of that particular acid, but as far as I know every single acid will react with metal. I would think that aluminum tubing is not the best choice b/c your conc. acid will break down to H2 and other things. Probably what happened in your case was that nitric acid reacted with Al foil causing enough heat to melt the tubing, so if you use some other material for your stoppers you should be fine, but then again I am not speaking out of experience, that’s simply my theory.

[Arthis]

Hue, he, ho ! If you had read my previous post, if you had search a bit before presenting us your "theory", then you would have been aware of the passivation phenomenom. Your theory is wrong.
And do you really think it could have made the Al melt ?

Maybe you should get informed before sending posts.