chemrox
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large capacity soxhlet issue
I have a large capacity soxhlet. The side mounted extractor barrel holds 2 L. (This is different than the 5L one I mentioned previously). Anyway,
I'm extracting Reed Canary Grass with ether. The issue is the siphon tube doesn't drain the extractor. It drains slowly enough to maintain the
extractor at always full. This is great for extraction but makes emptying the apparatus a pain. I wonder if the drain tube is too large or too
short? Anyway I solved the problem once by some vigorous finger tapping. That's one cycle down-many more to go...3L is too small a flask for this.
5L would be appropriate.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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Zan Divine
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It sounds like the drain tube is a little too tall. The Soxhlet must be able to fill to a point higher than the top of the bend in the drain.
An inelegant solution is to incline the extractor slightly to bring the bend a little lower. The elegant solution, with a torch, is not simple but it
can be done...flatten the curve in the drain tube to lower it a few mm.
[Edited on 6-7-2012 by Zan Divine]
He who makes a beast of himself gets rid of some of the pain of being a man. --HST
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Zan Divine
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The other thing that you want to make sure of is that the solvent in the body has free and easy access to the base of the drain tube. A layer of glass
wool (or similar) a quarter or half inch high should be placed at the bottom. You probably already did this, but in case you haven't, you should. Of
course, if you actually have the real soxhlet filter tubes, this isn't a concern.
Sometimes just increasing the reflux rate can change the dynamics of starting the siphoning process. I realize that you are using Et2O and that you
make not have a lot of headroom in this area.
[Edited on 8-7-2012 by Zan Divine]
He who makes a beast of himself gets rid of some of the pain of being a man. --HST
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Arthur Dent
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A trick I do when I use my sohxlet is to wet the extractor area with the solvent before assembling the apparatus. That way when I put on the heat and
the solvent begins to flow, the cotton plugs at the bottom and at the top have already settled and don't expand too much and disturb the threshold of
the drain tube.
As for the real soxhlet thimbles... never used them, this is truly the hardest-to-find chemistry consumable imaginable. The only time I found some was
in Sigma Aldrich's catalog... eer... nevermind!
Robert
--- Art is making something out of nothing and selling it. - Frank Zappa ---
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chemrox
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Back again with a different plant and same solvent, ether. There's no issue with flow through the system. This extractor is way big for thimbles and
I have left the plants in a crumbled but not powdered condition so a grate at the bottom hold nearly everything back. The bend in the tube is still
below the max height of the liquid in the vessel. Zan's answer intrigued me at first because the motion in leaning the apparatus slightly always
makes the liquid fill the siphon just past the overflow point. However, in principle there can't be siphoning until the height of the liquid in the
vessel is higher than the bend in the tube. I.e. the condensed solvent fills the vessel up the siphon bend and then it's supposed to siphon. Instead
it pours over in a much slower stream ~ the rate of condensation. Maybe I should add excess heat to the flask and try to make the liquid in the
extractor exceed the leak down rate. Also I have allowed the extractor to be a little cooler than the rising vapor. I try to keep just below the vp
of the ether. What do you guys think of higher heat? (With ether this means shutting down at night).
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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chemrox
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Interesting addendum. I decided having it stay full wasn't such a bad idea. A mistake I made was overheating the holding vessel and almost
evaporated 2 L of ether. I lowered the heat. I left the vessel full and after an hour (or less) it siphoned anyway. The vessel needs to fill to a
certain height above the bend and over she goes. Adding heat to the flask and lowering heat in the vessel seemed to cure the issue. Tricky little
bastard. Zan is right on.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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feacetech
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Quote: Originally posted by Arthur Dent  |
As for the real soxhlet thimbles... never used them, this is truly the hardest-to-find chemistry consumable imaginable. The only time I found some was
in Sigma Aldrich's catalog... eer... nevermind!
Robert
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Whatman make extraction thimbles but they aint cheap
I like the soxhlets that have a the side arm as opposed to the siphon bend
like the diagram here http://www.techknow.org.uk/wiki/index.php?title=Soxhlet_Extr...
I hope you werent extracting a mono amine from that grass :p
big extactors you have bet they cost a bit?
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quantumchromodynamics
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extraction question
When done chuck the solvent and keep the goods? Would petroleum either maybe work even better?
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Mildronate
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Chemrox can you post picture of your soxlet?
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zed
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When I was in highschool, I had an acquaintance who built a cigarette smoking machine. Used a vacuum pump to provide low grade suction, and a
condensor fashioned from couple of glass flasks, to catch the tar and nicotine. He accumulated an impressive quantity of crud, pretty quickly.
Just lit up the cigarettes, and let the machine convert them to CO2, H2O, and the Alkaloids of interest.
Seems to me, Canary Reed grass, might be amenable to the same method of extraction. Either giant "spliffs" or a tube furnace type arrangement,
might be used to "smoke" the alkaloids out, while a vacuum would pull the vapors into a chamber set up for condensation.
[Edited on 30-5-2014 by zed]
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