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Author: Subject: Sep funnels and vacuum?
Refinery
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[*] posted on 13-6-2020 at 10:22
Sep funnels and vacuum?


Do separatory funnels generally withstand vacuum? I need to do some vacuum filtrations with larger volume liquid and I thought I could use sep funnel as receiver and drain the liquid as needed. Based on their shape they should withstand reduced pressure. Obviously the vacuum needs to be settled before operating the sep valve, unless unwanted things will happen.
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monolithic
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[*] posted on 13-6-2020 at 11:00


I've seen them used under vacuum like in this video https://www.youtube.com/watch?v=lBNhu4kJ4Mc

That said it's probably a good idea to use a smaller separatory funnel without any visible voids in the glassware.
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[*] posted on 13-6-2020 at 12:18


They should be able to take it.
Sep funnels with a ground standard taper bottom joint are made to function as an addition funnel too, so they have to be made to take vacuum as this happens a lot with addition funnels.

The other ones (drip tip bottom, no joint) seem pretty much the same, but I agree that you should check the glass for voids and defects.

If we're talking about a 250 ml or a 125 or less then I wouldn't worry at all.
Bigger is riskier, but as you pointed out they do have a good shape for vacuum, so they ought to be okay.

I'd be reluctant to evacuate a 2 liter or bigger though.
That might be okay for all I know, but I wouldn't be eager to test it out for myself without lots of duct tape.




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wg48temp9
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[*] posted on 13-6-2020 at 12:41


The usual separation funnel with no flat areas or defects should be fine but check it first empty just in case.

Old cathode ray tube with almost flat 6in front faces and made with glass no thicker than the average separation funnel contain very good vacuums.

cathodraytubejpg.jpg - 180kB




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Refinery
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[*] posted on 13-6-2020 at 12:57


I presume that safety margin requires that sintered glass filtering funnels can generate up to about 1kg/cm2 vacuum pressure with sufficient pump.
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wg48temp9
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[*] posted on 14-6-2020 at 00:00


Quote: Originally posted by Refinery  
I presume that safety margin requires that sintered glass filtering funnels can generate up to about 1kg/cm2 vacuum pressure with sufficient pump.


Not on the joint to the seperation funnel if its like this one:

sinfil.jpg - 5kB




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[*] posted on 14-6-2020 at 05:28


It's like this. With ground joint and vacuum connector.

CG-1406-E__00293.1445481732.500.750.jpg - 19kB
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[*] posted on 14-6-2020 at 05:36


When filtering there is a lower limit to pressure usually determined by the boiling point of the liquid
(and ambient temperature)




CAUTION : Hobby Chemist, not Professional or even Amateur
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