BILLBUILDS
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would this sort of pump be useful for vacuum distillation
would a pump like this be suitable for vacuum distillation or is it only designed for vacuum filtration?
http://www.ebay.com.au/itm/151238475938
if not could someone show me a cheap example of what would suffice
thanks
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AvBaeyer
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I have one very similar (at least in appearance). I use it only for vacuum distillations and after many runs it will still pull 0.050-0.075 mm Hg
vacuum. I almost always have to bleed it as it pulls to well. The oil capacity is small so oil needs to be changed after every couple of uses. Because
of the small oil capacity, it is NOT suitable for vacuum filtration. It will go to hell pretty fast. If you bleed it too much to try to use it for
filtration it will make way to much noise and belch oil fumes. My pump operates best below 5 mm Hg.
For vacuum filtration I suggest you try to find a used recirculating aspirator pump. They are somewhat pricey but worth every dime. It will also work
well distillations at 10mm Hg and up. If you have cheap water, you could just attach an aspirator to a sink faucet for filtration.
AvB
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Sulaiman
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At about 600 Pa (4.5 mm Hg), Water will evaporate cooling the bulk of it until it freezes.
The pump refered to has a rated pressure of 2 Pa, so a lot of air-leak OR a pressure regulation system would be required.
It also means that you would need cryogenic cooling for your condenser(s) for most solvents.
For us amateurs cryogenic cooling is somewhat inconvenient so distillations are best performed at reduced pressure but not at very low pressures.
So far, for vacuum filtration and 'vacuum' distillation I have been using my little vacuum pump http://www.ebay.co.uk/itm/Multi-Function-DC-12V-Micro-Piston...
even though I have a dual-stage rotary capable of <1 Pa.
The same constraints apply to vacuum filtration;
if the pressure is too low the solvent will boil.
CAUTION : Hobby Chemist, not Professional or even Amateur
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adk
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In addition to an Edwards RV12 pump (expensive), I use something similar to this as it is much smaller and can sit inside the fume hood and I don't
mind if it gets a bit trashed.
http://www.ebay.com.au/itm/Vacuum-Pump-2-Stage-for-A-C-Refri... acAAOSw241Ygb6a
I also have a -105 chiller to condense stray vapours and protect the pump seals and oil.
Rotary vane pumps are not suitable for filtration. Pretty much any low boiling solvent (less than 100C) is going to boil violently at room temperature
under a vacuum of this strength (<1 torr). Use a PTFE diaphragm pump for filtration/evaporation of solvents (Vacuubrand, KNF, Buchi etc)
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