gravityzero
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Vacuum Protection
The other day I noticed that the moisture trap to my rocker vacuum pump had all but exploded. In various reactions I've used the vacuum using only
the built in moisture trap for protection.
Using the vacuum without a real moisture trap has proven to be disastrous. I guess you would say I was being cheap, but now I had to pay around
$80.00 to get replacement parts for the vacuum pump.
Apparently a gas vapor was created from something that had soaked the moisture trap and expanded the plastic enclosure to the point the thread split
away. The entire hard plastic was fairly warped/melted. Very concerning.
Anyways, my idea is to protect the vacuum with at least one Erlenmeyer side arm flask. I will run a glass tube through a stopper to the bottom of the
flask, for the inlet. The side arm will be connected with a tube leading to the pump.
I think I might even do this in series, using two flasks. The first could use a liquid to capture any vapors, then maybe through an empty flask, or
possibly one using drierite or drying agent.
Without getting too specific on any one given procedure, comments and thoughts on this setup are welcomed and greatly appreciated, for sure.
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sargent1015
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I am hoping that you cool your trap with ice, dry ice, running water, etc. Otherwise, most solvents will blow right past the trap and into your pump!
Btw, two traps are indeed better than one!
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gravityzero
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I don't have good access to dry ice and where I do, it can be fairly pricey and hard to handle/store.
I will try using ice cold water, and create an ice bath for the flask, followed by an empty flask.
When distilling solutions that contain solvents, I normally use an longer condenser to fully condense before exiting the vacuum connector. It seems
no matter, there is always stuff that escapes the other side.
Thanks so much for the info.
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sargent1015
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There will always be some vapor, but the two trap idea is best. If I may ask, what typical solvents are you pulling off?
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gravityzero
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I'm working with dcm, acetone, mek, toluene, ether.
Sometimes I make my own ether with Etoh + H2SO4.
Sometimes I try extractions of natural products, ie piperine from ground peppercorns. Caffeine extracts. Extractions from seeds. Extractions on
natural products. I've very interested in natural, semi-natural compounds.
I'm also interested in Hydrogen engines. H2O electrolysis and the like. I'm still a little new to chemistry. I'm self taught what I do know and
didn't really take any upper level chemistry in college. I wish I could go back someday.
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starman
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With the exception of toluene all highly volatile solvents.No need for vacuum stripping unless you are dealing with some very heat sensitive
compounds.
I would suggest atmospheric distillation for the bulk and if you want to vacuum strip the residue use an aspirator on the residue.
Really taking off anything as volatile as ether with mechanical vacuum will require at minimum dewar with dry ice/acetone.
Chemistry- The journey from the end of physics to the beginning of life.(starman)
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gravityzero
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I should correct by saying that when I am simply redistilling a solvent, like after drying, I do not use a vacuum.
Most of the time, such as when making ether, I am not using a vacuum pump. Now let’s say that I have a compound that needs vacuum filtration and a
solvent is the carrying agent. That is when I generally apply vacuum.
Let’s say I am distilling of a natural product, or modifying a natural product that is sensitive to heat. I usually will reduce atmospheric
pressure, so the volatile compound is not compromised.
I recently came across a rotovap. I will probably incorporate a vacuum when using it to distill off compounds.
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tsukasa
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Usually aspirator is used for vacuum filtering. A membrane pump (also called diaphragm pump) is suitable for both rotary evaporator and vacuum
filtering, because all of it's parts, that contact with solvent are made of inert materials (like Teflon). Rotary-vane pump (according to my own
experience of disassembling one) chamber is made of steel (and is prone to corrosion), vanes seems look like glass-fiber laminate (it is not resistant
to some aggressive solvents too).
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Waffles SS
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Do you have access to CO2 Cylinder?if yes then you can make your own Dry ice
http://www.nuffieldfoundation.org/practical-physics/making-d...
http://www.wikihow.com/Make-Dry-Ice
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