Picric-A
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Hand Vaccum pumps
Has anybody had any experience with them?
I was thinking of buying one for use with my rotovap- a couple of squeezes now and then to hold a nice vaccum in the apparatus instead of constant
running water.
It also beats buying a £100 mechanical pump... They are ~£25 on ebay but i have no idea how much of a vaccum they can hold and whether or not they
will break after 2 mins on contact with something like EtOH vapour....
Most of them on ebay seem to be related to mens .... enlargers 
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bahamuth
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Think you will need a somewhat bigger vacuum source than a hand pump for a rotavap, been working a lot with those
Read somewhere on the net, and know people here at home have been using old refrigerator pumps as a vacuum source, some say they give pretty decent
vacuum to.
And they will supply pressure on the "outlet" if you ever need that..
Hope this helps..
Any sufficiently advanced technology is indistinguishable from magic.
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entropy51
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Like almost anything else imaginable, it has been discussed on the forum, most recently just a month ago: Quote: Originally posted by entropy51  | | A hand pump is OK for small filtration jobs, but for distillations I don't think the vacuum will be steady enough and eventually your hand will fall
off from exhaustion. |
You need either an aspirator or a vacuum pump for a rotovap. And don't try either of
those for an ahem, enlarger.
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Picric-A
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Sorry not for searching more, i agree it will be very tiring holding a decent vacuum.
I only have a small bibby rotovap but nonetheless it would be a lot of effort.
I will look into buying a bigger pump.
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hissingnoise
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| Quote: Originally posted by bahamuth |
Read somewhere on the net, and know people here at home have been using old refrigerator pumps as a vacuum source, some say they give pretty decent
vacuum to.
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'Fridge-comps need efficient corrosives/moisture traps to get any kind of longevity---a water trap for basic vapours followed by a H2SO4 or two in
line. . .
Condensates in the works will destroy them in fairly short order!
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aonomus
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Not to mention that fridge compressors also require oil like any other compressor. Fridge compressors aren't made to retain their oil, instead they
recirculate it along with the refrigerant because it was designed with the closed loop in mind. The oil shouldn't go anywhere, so it will eventually
make it back into the compressor in a refrigeration system.
That being said, you can try the compressor as a vacuum pump, but be prepared for oil loss on the output (have something to catch the oil, it will be
messy), and be very careful as to what vapours you pump through it.
Personally I'm getting a plastic aspirator which in combination with a decent pump should get good enough vacuum for filtration and distillation.
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hissingnoise
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If your water-supply is un-metred and cold (in Toronto?), its normal pressure and a metal aspirator is the perfect combination. . .
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aonomus
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I don't feel like wasting water (which is metered) when I can simply run a good pump with water and ice to get good vacuum.
Heck, during winter I can take a bucket half full of water and fill the rest with snow to get *really* cold water without wasting any more energy on
that.
Same idea with water condensers, don't waste tapwater, just recirculate and cycle out the water every so often to prevent bacterial/algal growth.
Those handheld vacuum pumps will fail pretty quickly, so you'd be better off buying a real vacuum pump if you want one...
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DJF90
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Thinking for just half a second about the intended application makes a hand pump unsuitable for one reason... no, not corrosion due to solvent in the
pump.
So you're pumping away, trying to create a vacuum, and as you're removing solvent (i.e. vapourising it, creating a vapour pressure), you're killing
the vacuum you're creating with solvent vapour.
You NEED a mechanical pump of some kind.
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worldspawn
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Argh. I've been scouring the net for a week or so trying to find a used vacuum pump, but I've come up with nothing. These things are expensive.
*edit* And the cheapo medical aspirators have their sale regulated by the FDA.
Two options: either use a pump and aspirator or be ready to spend $200+.
[Edited on 5-11-2009 by worldspawn]
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dann2
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Hello,
Hand operated, homemade pump at his link.
http://scitoys.com/scitoys/scitoys/aero/vacuum/
Have not made it myself so don't know anything about it.
Dann2
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