thelonious
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Distillation question
I'm almost done piecing together my setup for distillation, and I plan to start by distilling dichloromethane out of paint stripper. Since I don't yet
have any kind of pump, I'm thinking of running cold tap water through my condenser (30cm West condenser), and as a result, would be performing the
distillation indoors. I don't particularly want my basement filled with dichloromethane gas, so my idea is to connect a rubber tube to the hose
connector on my vacuum take-off adapter. The other end of the tube would be immersed in water. By looking at the bubbles coming out of the tube, I
would be able to see how much (if any) dichloromethane is escaping my setup uncondensed.
Would this work? Is there any obvious flaw to my plan?
Thanks for helping a noob out
PS. I would grease the joints with vaseline to minimize any gas leakage from the ground-glass joints of my setup.
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cyanureeves
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i bet tap water is cold enough because i did it straight out of the can and it distilled at very low heat.
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Sublimatus
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If the whole setup is really air-tight, just watch out at the end of the distillation. When you shut off the heat the internal pressure will drop,
and then there's the potential for the water to get sucked back up through the hose into your receiving flask.
Also, you might get vaseline leeching into the system. I recall using it for a distillation once and it got pulled out of the joints. Granted, DCM
boils at a lower temperature than what I was distilling, so maybe it was just a temperature thing.
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watson.fawkes
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Quote: Originally posted by Sublimatus  | | When you shut off the heat the internal pressure will drop, and then there's the potential for the water to get sucked back up through the hose into
your receiving flask. |
This was my concern. Suck-back could also occur if there's some kind of failure that
leads to unexpected cooling. The solution is a trap, which is just an empty flask, a double-hole stopper, and a pair of hoses; insert it in the
bubbler line. If water does suck back, it ends up in the flask instead of the collection flask (or worse).
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kavu
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Placing the receiving flask into an ice bath should take care of the problem. You will need a CaCl2 guard tube attached, if you want to exclude the
possibility of moisture condensing into the distillate. Trapping DCM in water is a pain to dispose, you can't (or you shouldn't) pour it down the
drain as it contains organic halides.
[Edited on 8-7-2012 by kavu]
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