Sciencemadness Discussion Board - Use of Scrubber in Atmospheric Distillation

Use of Scrubber in Atmospheric Distillation

LifeisElemental - 23-7-2014 at 08:14

Hello all!

I apologize if this is a violation of UTFSE but I had looked and was unable to find any discussion on this. (Likely my own error)

I plan to distill nitric acid at atmospheric pressure without a vacuum. I am worried of the possibility of NO₂ gas being released so I am considering adding tubing connecting the vacuum adapter to an alkaline solution.

I have created an image depicting the apparatus I plan to construct. Would this be functional?

numos - 23-7-2014 at 08:49

If you do this reaction outside or in a fume hood, nitrogen oxides are not a problem. If you want to do this inside without a fume hood you may want to use a scrubber, but I suggest simply doing this reaction outdoors.

But yes that system would work well as a scrubber.

hissingnoise - 23-7-2014 at 08:51

A scrubber is neither necessary nor desirable in this instance.
A large proportion of evolved NO₂ will dissolve in the distillate with very minor quantities escaping . . .
Good ventilation is advisable, though!

gdflp - 23-7-2014 at 08:52

That would be functional, the nitrogen dioxide will react as follows 2NO2 + 2NaOH --> NaNO3 + NaNO2 + H2O. As long as the reactants are cooled before hand and the distillation is not allowed to surpass 83°C, only very small amounts of NO2 are formed. Even with the alkaline scrubber, I would not do the distillation indoors unless you have a fume hood.

Metacelsus - 23-7-2014 at 09:53

Watch out for suckback; if you use a scrubber you should add a trap.

Even without vacuum this is still an issue, due to gas pressure changes with temperature.

[Edited on 23-7-2014 by Cheddite Cheese]

LifeisElemental - 23-7-2014 at 16:28

Thank you all very much for the advice! I had actually planned to perform the reaction indoors and no longer will.

Quote: Originally posted by Cheddite Cheese

Watch out for suckback; if you use a scrubber you should add a trap.

Even without vacuum this is still an issue, due to gas pressure changes with temperature.

[Edited on 23-7-2014 by Cheddite Cheese]

If possible, could I get an idea of what a trap is? It's a concept I have a very difficult time of grasping. I've searched "what is a trap" and similar questions and have not found anything that clicked with me.

arkoma - 23-7-2014 at 17:16

A=reaction vessel (in your case the vacuum takeoff would be this)

B=empty flask

C=Neutralizing solution.

Part "B" catches any backflow from a pressuredrop and prevents it from entering into the receiving flask. NaOH and HNO₃ suddenly mixing would not be good. Flask "B" would catch and prevent that from occuring.

edit--fixed bb tag

[Edited on 7-24-2014 by arkoma]

LifeisElemental - 24-7-2014 at 04:12

That is a great explanation Arkoma! Thank you all again, I will likely not plan to carry out this reaction for a short while until I acquire some adequate ventilation. However, I greatly appreciate the kind advice on the topic.

Praxichys - 24-7-2014 at 04:38

For NO2, just get a length of clear plastic tubing and shove it down a drain until it's past the trap. You could also run the tube outside. No sense in wasting chemicals scrubbing something that you're not releasing a whole lot of to begin with.

Vapors from nitric acid usually aren't a problem during a distillation. It's the disassembly of the apparatus afterward that is going to release the most. Keep that into consideration. A fume hood or outside is best.

The Volatile Chemist - 24-7-2014 at 05:28

Have fun! Post some pictures!

plante1999 - 24-7-2014 at 05:33

The picture reminds me, Anyone here tried the lab scale coal pyrolisis? If so, got pictures? I wanted to do the experiment and even ad bought a lot of small pieces of bituminous coal for it but time was faster then I.

[Edited on 24-7-2014 by plante1999]

[Edited on 24-7-2014 by plante1999]

Magpie - 24-7-2014 at 07:33

Quote: Originally posted by arkoma

Very nice sketch. But for clarity: to prevent suckback the trap B functions by keeping the solution in C from sucking back into A. Of course it also works the opposite way too, as you state.

arkoma - 24-7-2014 at 07:42

can't take credit for sketch, kiped it from this article. First clear image I found that could apply to LifeisElemental's question

chemrox - 24-7-2014 at 14:47

Can't you run a long hose out a window somewhere? I used to do this before I had a hood. Also a fan in a window could serve for NOx

The Volatile Chemist - 26-7-2014 at 12:03

The hose down the drain or out the window is my fav. idea. In the confined space I have, it's kinda necessary at times. As for buffer flasks, has anyone actually seen a situation where they saved the solutions from mixing? I've rarely used them, so I don't know if they're necessary all the time or not...

aga - 26-7-2014 at 12:14

Quote: Originally posted by The Volatile Chemist

buffer flasks, has anyone actually seen a situation where they saved the solutions from mixing?

Funny you should say that.

Today i used a buffer flask in the nitric nurdrage with copper thing, as the last time i got a bottle of Green and a bottle of Blue.

So i used a buffer flask today, and ended up with three bottles.

Green, Blue and Empty.