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Author: Subject: Vacuum Distillation of Aniline
Texium
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[*] posted on 3-6-2020 at 11:26
Vacuum Distillation of Aniline


I successfully distilled some old, dark red, commercial aniline under reduced pressure.

The full write up is on my blog here.

I also posted a quick time-lapse video of the distillation to YouTube, which can be viewed here!



Screen Shot 2020-06-03 at 12.40.18 PM.png - 3.3MB Screen Shot 2020-06-03 at 12.47.38 PM.png - 2.4MB IMG_8362.jpg - 480kB

Putting pretty liquids in little brown bottles is always so satisfying.




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Fery
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[*] posted on 3-6-2020 at 12:25


Hi Texium, I read you blog where you described a problem with bumping. In vacuum distillation there is a big temperature gradient between bottom layers and surface of the liquid in the distillation flask (bottom heated, surface cooled by evaporation). When these layers mix accidentally it causes bumping. To prevent that, it is necessary to insert a capillary which introduces steady stream of tiny bubbles into the bottom which mixes the flask content, or using magnetic stirring also prevents bumping. I see on your picture that you distillation flask is not in the center of the heating plate so assume I correctly that you didn't use magnetic stirring (otherwise you would place it into the center) ? Boiling stones do not work in vacuum sufficiently (you used them according your blog).



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Texium
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[*] posted on 3-6-2020 at 15:10


Yes, it’s true that I did not use stirring, and that I should have. The reason that I didn’t use stirring was because I didn’t want to ruin any of my PTFE stir bars by permanently staining them with the polyaniline gunk. I don’t have many stir bars right now and most of them are very nice. If I had a pack of small cheap ones on hand I would have definitely used one.



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draculic acid69
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[*] posted on 3-6-2020 at 18:36


Wrap a nail in teflon tape for a disposable stir bar. This is assuming that the aniline won't do something with iron like decompose or polymerize further. If u wrap it well enough it should be fine but nothing is 100%. I wouldn't trust this for distilling hydrochloric acid or a h2so4 solution but maybe distilling a base will be ok.
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[*] posted on 3-6-2020 at 22:23


I really must practice my vac distilling. I've had serious issues with bumping so far. I made a bleeder tube from capillary, but haven't had time to test it yet.

Shouldn't stir bars be available in china by the kilo? I ordered a bag that has like 30 different bars, but I usually just use the one I go with.
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[*] posted on 4-6-2020 at 05:23


draculic acid69 that's very cool idea, wow, genius, simple, cheap !!!
perhaps only very short piece of nail should be used as the flask is RBF or better some iron piece with a shape thicker in the middle which allows better rotation or more turnings of the tape in the middle and less on the nail ends...




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