mycotheologist
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Any simple alternatives to vacuum pumps?
I have an immediate need to do some vacuum filtrations, I have a vacuum flask + Hirsch funnel but I don't have a vacuum source. Are there any tricks
for providing a bit of vacuum with household items? I only need to hold the vacuum long enough to filter my product and do one or two quick washes.
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garage chemist
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For several years, I have done all my filtrations and vacuum distillations with an aspirator. It's the best vacuum pump for the amateur because it
isn't ruined by vapors and fumes.
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Lambda-Eyde
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Quote: Originally posted by garage chemist  | For several years, I have done all my filtrations and vacuum distillations with an aspirator. It's the best vacuum pump for the amateur because it
isn't ruined by vapors and fumes.
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...And it's cheap! A 10€ plastic aspirator sure beats a 200€ pump that needs constant attention, cleaning and maintenance. I am however jealous of
UC's teflon diaphragm pump...
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mycotheologist
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Thanks a lot, I didn't know about these cheap aspirators until I saw your one in your picture Lambda-Eyde. Just need to figure out where to get one
now. Are they only used in labs or do they have mundane uses? In other words do I have to order it from a lab supplier or can I find one at a plumbing
shop etc.?
EDIT: I can only find lab supply sites selling them so I'm guessing I have to just order it. This ones cheap:
http://www.justplastics.co.uk/product.php?id=3795
but they don't say what pressure it provides. They say its autoclavable, I have no idea why someone would need to autoclave one of these things.
EDIT2: Take a look at that justplastics site, they sell plastic versions of all kinds of things like Buchner funnels, sep. funnels and vacuum flasks.
I wonder why they don't make plastic quickfit apparatus. For example, a HDPE distillation kit would be useful for distilling plenty of low BP liquids.
Some of their cheap instruments are made of polymethylpentene, I don't know what chemical resistance properties its used in cookware and autoclavable
tools so it must have good thermal resistance.
[Edited on 8-12-2012 by mycotheologist]
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smaerd
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I'm very weary of plastic laboratory apparatus and always go for glass when possible. Just because you can boil/heat something once in a plastic flask
doesn't mean it will really hold up over time. Especially when using a variety of solvents. I think a lot of the idea behind plastic equipment is it
is disposable.
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Lambda-Eyde
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| Quote: Originally posted by mycotheologist | | Thanks a lot, I didn't know about these cheap aspirators until I saw your one in your picture Lambda-Eyde. Just need to figure out where to get one
now. Are they only used in labs or do they have mundane uses? In other words do I have to order it from a lab supplier or can I find one at a plumbing
shop etc.? |
I can't think of any uses for an aspirator outside of a laboratory. Check out eBay (shipping small items from the states isn't very expensive).
That one looks identical to the one I have, I'll say go for it. Plastic aspirators are much better than metal or glass ones IMO. Metal corrodes, and
glass breaks...
| Quote: Originally posted by mycotheologist | | EDIT2: Take a look at that justplastics site, they sell plastic versions of all kinds of things like Buchner funnels, sep. funnels and vacuum flasks.
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If you mainly do aqueous inorganic chemistry, then a plastic büchner funnel might be just the thing for you. Steer clear of the other stuff. Glass is
superior in almost every way, except that it's prone to breaking and doesn't like F<sup>-</sup> very much. But that's it. Those sep
funnels are even more expensive than glass ones.
| Quote: Originally posted by mycotheologist | | I wonder why they don't make plastic quickfit apparatus. For example, a HDPE distillation kit would be useful for distilling plenty of low BP liquids.
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Oh, but they do. The reason they're not popular is because glass is much cheaper and more convenient. Could you imagine distilling DCM in a
plastic apparatus? The only reason such apparatus exists is for niche uses, such as distilling HF or other insane stuff like that.
| Quote: Originally posted by mycotheologist | | Some of their cheap instruments are made of polymethylpentene, I don't know what chemical resistance properties its used in cookware and autoclavable
tools so it must have good thermal resistance. |
PMP, or TPX is a crystal clear plastic with good chemical and thermal resistance and offers a nice alternative to glass, but again, if you ever
decide to take up organic chemistry you don't want to constantly worry about chemical resistance.
| Quote: Originally posted by smaerd | | I'm very weary of plastic laboratory apparatus and always go for glass when possible. Just because you can boil/heat something once in a plastic flask
doesn't mean it will really hold up over time. Especially when using a variety of solvents. I think a lot of the idea behind plastic equipment is it
is disposable. |
I mostly agree, but the main argument for plastic labware is the niche uses as already mentioned.
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chemrox
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I found a glass aspirator on ebay that I had seen in a catalog once. I wish I could find the manufacturer name. This little item pulls 1 < 10 mm.
"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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Endimion17
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Buy a cheap plastic hand vacuum pump, such as the ones for sucking the air out of those bags people put clothes in, to save space in wardrobes.
Buy a large (>10 L) glass container and some aquarium stopcocks and pipes. The idea is to suck out the air as much as possible and to use the
container as a "buffer" for vacuum you can occasionally "power up" with your pump.
I use such system for vacuum filtration.
Aspirators are great, but they do waste a lot of water.
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lolcat
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how strong should the water flow be for an aspirator? My thoughts are either to buy an aquarium pump, like one I use to pump cold water through my
condenser, although I don't think that will give much vacuum. Else I am thinking of buying a 10 gallon bucket from home depot and attaching a nozzle
at the bottom that will feed into the aspirator, I would think that that would give greater vacuum than the small aquarium pump.
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S.C. Wack
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Do not do this. They are worthless unless you are evacuating test tubes. Instead, modify a modifiable version of an obscure item known as "bicycle
tire pump". Considerably more capacity; not made of plastic.
Or buy an advanced version for the same price: http://www.sciencelabsupplies.com/Hand_Pressure_and_Vacuum_P...
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Endimion17
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That's why large "buffer" containers are for. We're not talking about very low pressures here. It's about a steady supply of partial vacuum.
Bicycle tire pumps with inverted pistons are something that can be quite lousy, too. I'd go above 25$. However, the pump in your link seems quite
durable.
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lolcat
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how do you run water through your aspirator? Is it connected directly to a faucet, or is it connected to a pump?
| Quote: Originally posted by garage chemist | For several years, I have done all my filtrations and vacuum distillations with an aspirator. It's the best vacuum pump for the amateur because it
isn't ruined by vapors and fumes.
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mycotheologist
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| Quote: Originally posted by lolcat | | how strong should the water flow be for an aspirator? My thoughts are either to buy an aquarium pump, like one I use to pump cold water through my
condenser, although I don't think that will give much vacuum. Else I am thinking of buying a 10 gallon bucket from home depot and attaching a nozzle
at the bottom that will feed into the aspirator, I would think that that would give greater vacuum than the small aquarium pump.
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I have one but the water flow is really weak. The 10 gallon bucket is a good idea. To increase the water flow rate, you could use a plate (It'll have
to be almost the same diameter as the bucket) to make a piston, you just float the plate on the surface of the water then put a heavy weight like a
cinder block on the plate. This is what I'm gonna do, thanks for the idea. I'm gonna use one of those big paint buckets and make a really small
opening (about 1/4 inch) and force some 1/4 inch braided PVC hose through it and use window sealer caulk or something to seal it in place. That would
be easier to install than a nozzle I'd say. I don't know what to use as the plate yet. Maybe I'll cut the sides off the lid of the paint bucket. Whats
cool about this idea is your using your own energy (the energy required to lift the weight) to create the vacuum source, as opposed to relying on
electricity or water pressure from the tap.
[Edited on 11-12-2012 by mycotheologist]
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atomicfire
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I use the compressor from an old mini fridge. I had a local heating and cooling place take the coolant out and this thing works to get some decent
vacuum for simple distillations.
I have used a self recirculating water aspirator in the past. I found an old water feature pump (like for outdoor things) and used it to pump water
around in a closed environment and through the aspirator. I didn't get much vacuum though, probably because the pump wasn't very big.
ban DHMO
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Houngan
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Aquarium Pump
I modified a aquarium air bubbler pump to suck instead of blow. I bought it online for about $15 and used a little "Knead It" TM so the vanes were on
the opposite side of the holes. I can get 100 mm Hg of vacuum from it. If you want I can post a picture.
The spice must flow.
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virgilius1979
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Could distillation glassware brake due to vacuum inside ? I have some 1000 and 500ml flasks and I wonder if they are able to withstand a 50 micron
vacuum.
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SM2
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if your really desperate, you can have a poor man's aspirator as part of a water-bed refill kit.
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GammaFunction
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As a McGyver'ish idea, could you take a large flask with a stopcock, boil water in it to fill it with water vapor and displace the air, then close the
stopcock and let it cool, bringing internal pressure down to the vapor pressure of water. Then connect the other end of stopcock to filter flask and
open. Like this video.
Using a pressure cooker, one could make a pretty big reservoir of vacuum.
Another McGyver trick would be this siphon.
edit: with the water vapor idea, maybe you could use the filter funnel as its own source of vacuum by setting it up with a bit of water in the bottom,
heating it to fill it with water vapor, and then pinching a rubber tube attached to the flask's vacuum port as you shut off the heat. The risk is
subjecting the funnel contents to some heat and steam.
[Edited on 5-3-2013 by GammaFunction]
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violet sin
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if your gonna go full McGyver: 1 small tupperware, 1 aquarium pump, 1 nylon hose barb, a few feet of hose and some epoxy. could you not cut 3 holes
in a small Tupperware container. use one for for a hose barb on the outside that goes to nothing inside. use one for a thru hole from the aquarium
pump to outside, and use the last one for the power cord of the pump. idea is the pump inside the container evacuates to the outside freely. but
with all the air going out, some has enter the system. your lonely hose barb becomes a vacuum source of questionable power.
basically changing the dynamic by providing an extra barrier. pump becomes vacuum. this is likely a lousy idea but I will try it this evening any
way. 2 or 3 spares from our fish so why not. I know that the pump will be enveloped in any vapors.
likewise you could use a threaded pvc pipe as a filter by putting the ppt/sol inside and blow in air also after sealed. forcing water out, through a
filter paper over a few holes in the bottom cap. really not pretty ideas but for some one who has little funding it may prove useful.
if either works well with a crappy 15$ aquarium air pump I would be quite pleased and share my results. but it may ultimately turn out to be nothing
more than a couple crappy ideas to wipe from the notebook.
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Organikum
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This aspirator you looked out is very well suited for your needs, I have the same and used it for quite some time, no problems. I now use a HAAKE
aspirator which I got for very cheap what was luck at this is a rather high end item normally out of my reach. For higher vacuum I use a very cheap
one-stage rotary vane, chinese what else, bought at Ebay. Although this pump has no ballast vent it also works without problems and by using a simple
Dimmer (chinese, Ebay you guess  ) I can control speed (and noise) from 100% to
about 50%. Using the aspirator as a forepump inline before the rotary vane the performance of a two-stage rotary vane is available satisfying all my
needs and more. Not bad for less then 70€.
So I say go for the plastic pump, price is very well too, I paid more for mine (plastic one) times ago.
/ORG
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blogfast25
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I've got no running water in my lab (I use containers and a defunct water cooler as 'running water', and a big bucket as 'sink') and recently bought a
mini-vacuum pump on eBay UK (advertised as "- 20" Hg", which isn't very low). It works well for vacuum assisted filtration but you need a good seal
between the Buchner and the flask. About £30, including power supply. A bit noisy for my liking, though.
[Edited on 5-3-2013 by blogfast25]
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jsc
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Two words: MITY VAC !!!!
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blogfast25
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'Splain?
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watson.fawkes
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It's actually one word: Mityvac®.
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blogfast25
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Hmmm... not a particularly great way of creating vacuum, if you need some decent L/min capacity...
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