Fyndium
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Erlenmeyer vacuum filtration?
How much vacuum can be applied to erlenmeyer flasks for vacuum filtration? Some people use specific rounded erlenmeyer vacuum filtration flasks for
this purpose, which apparently can hold full vacuum. I have used ordinary flasks, but I don't use actual vacuum pump, but a hand primer or cheap
chinese diaphragm pumps that don't deliver more than a fraction of vacuum, but filter still decently fast.
As NurdRage uses erlenmeyers for vacuum distillations, I presume that they can withstand at least some degree of vacuum safely?
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zed
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Ummm. Dunno. There are Erlenmeyers, and there are Erlenmeyers.
Erlenmeyer is the standard form... for Vacuum filtration flasks, but Vacuum filtration flasks are NOT standard Erlenmeyer flasks.
Filter flasks have thick, thick, thick walls. Ordinary Erlenmeyers, do not. Some, are downright flimsy.
I have some, that have screw-caps. I'm not even sure they can stand up to ordinary Chem-lab wear and tear.
They may have been designed as "culture" flasks. I have no faith in their strength and durability.
I'll pay attention to the flasks Nurdrage is using, the next time I watch one of his videos.
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Fyndium
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Let me help:
https://youtu.be/tYLlkTDstmo?t=213
The guy just casually vacuum distills stuff from erlenmeyers. NurdRage seem to use erleys almost exclusively, due to them being easier on hotplates.
I'd use erleys only because they do not need separate stand.
Mine are GG17 chinese and they appear somewhat heavy duty. I have 1 and 2 liter versions.
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zed
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His stuff looks sturdy. They are fairly small flasks. He's doing something innocuous under mild conditions. I don't see any problems.
Erlenmeyers aren't as strong as round bottom flasks. But, I have used them plenty.
I do keep in mind, that they aren't the strongest, and the "head space" is diminished.
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Fyndium
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I wonder if larger erlenmeyers can withstand lower vacuums, like up to 30% or whatever those small chinese diaphragms are able to produce? I've used
erleys plenty for suctioning due to how convenient they are. I have never applied true vacuum to them for obvious reasons. Largest I've used has been
2L, but what about for example 5L flasks? I've used RBF with stand support whenever I've needed full vacuum suction for the stickiest filtrates, but
for everything else the diaphragms are great.
The conical shape would be quite sturdy, but it's the bottom that implodes most likely. The erleys I've got has thickened midsection so they would
resist a bit more, but I would not dare ever do higher vacuum on them.
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draculic acid69
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There is a common rule/saying in chemistry that U should never apply vacuum to a non round bottom flask.this is commonly broken.vacuum flasks and
Erlenmeyers don't really count for this if being used as a filter.generally vac filtering doesn't get real low pressures.
[Edited on 15-4-2021 by draculic acid69]
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Fyndium
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Unless the solids form significant resistance. Filtering large crystals is like pouring water to a sink, but try to filter CaSO4 sludge.
I see a very good safety point on not ever applying vacuum to non-rbf and I follow this rule myself strictly when I use my main vacuum pump. In
general labwork involving multiple steps and people, common fool-proof practices are to be followed, because people are very bad at remembering all
kinds of non-written practices, but good at performing lobotomic routine work.
For hand pump and chinese cheapos, I get more liberal because they simply cannot generate more than 0.9-0.7 atm, while any good pump goes straight
down to millibar range. It slows down filtration somewhat, but it also has the benefit that general solvents like acetone, ethanol, chloroform etc. do
not evaporate straight to the pump, because they tend to do so even with the lesser vacuum. High vac pump will just boil the hell out of them.
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Belowzero
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There are 2 occasions where I've seen a heavy duty vaccuum erlemeyer implode/crack.
One of those events was quite scary since it exploded after imploding, sending glass flying.
Both of those cases involved deep industrial quality vaccuum and a moron operator.
Whenever using vaccum filtration and erlemeyers I always think about this event.
When I use my pump for filtration I always use a bleed to prevent the vaccuum from going too deep.
[Edited on 16-4-2021 by Belowzero]
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Praxichys
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A water aspirator at full bore can pull down to about 1.5 psia, which is ≈90% of a full vacuum and thus ≈90% of the force of a hard vacuum on the
flask. A strong vacuum pump left unregulated would hardly add additional risk.
The point is that flasks over about 500mL should be specifically vacuum-rated and either meshed or taped. All it takes is a little inattention or an
unexpected clog in your bleeder and there could quickly be a big problem. https://drs.illinois.edu/Page/SafetyLibrary/VacuumSafety
Imagine my concern finding items such as this for sale: https://www.amazon.com/5000ml-Vacuum-Suction-Buchner-Erlenme...
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