Fyndium
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Micro vacuum pumps?
Do small, micro scale vacuum pumps exist that have capacity of few hundred milliliters to up to a few liters per minute at max? These kind of pumps
would be small, cheap(ish), quieter and well enough for small exerimental setups, vacuum desiccator evacuations and so on. Full-size tabletop 400W
vacuum pump can suck a full-sized distillation apparatus with all accessories dry within seconds, while only a very small suction would be needed to
maintain it due to miniscule leaks.
Aspirators are one option and their benefit is running then directly from mains, so there's that.
Btw, why ebay aspirators state that max vacuum is 420mm Hg when aspirators with cold water should reach 30mbar?
[Edited on 2-8-2020 by Fyndium]
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outer_limits
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Maybe it's those aspirators capacity. My aspirator connected to the tap is pulling enough to boil water at 17 C
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Fyndium
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I distilled 194C BP stuff at 104C which indicates 70mbar vacuum with pump. Apparently the system was so leaky due to bleeder and poor fittings without
grease - and the pump had wrong oil - that it did not get it any lower, but I'll fix that later. I remember earlier boiling water easily at room temp
and I managed to freeze acetone with aspirator due to fast evaporation.
Nurdrage had that small water pump, I think I gotta see into that with aspirator. At least it is much more quiet and smaller than rotary pump and the
water is easy to keep cool with ice blocks.
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macckone
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You can modify an aquarium pump to work as a vacuum pump.
I use one of those for filtration and it would probably work ok for some other tasks but it won't pull a really hard vacuum.
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violet sin
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You can also get one of the cheap nebulizer air pumps for a few bucks at the thrift store. Mine was 4 or 5$. I switched the inlet and outlet tubes.
There was just a filter plug on the intake side, hidden in it's casing, and a weird clip that went to the back side... Snip!
The machine is set up to pump to you, so the pressure side went to the back side of a hose barb. Instantly converts to a vacuum pump with just a
screwdriver and a pair of pliers, that filter plug was snug in it. Total 4 screws lol.
I only separated one pre-glued hose connection, so it was pushed on and Cu wire twisted over for ease of disassembly.
  
It's only a plastic piston and one way valve so your not gonna get too nice of a vacuum, but 4$ ... It's enough for filtrations. Got to clean and oil
it after photos, it was a bit dirty.
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macckone
Dispenser of practical lab wisdom
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The nebulizer pump violet sin posted is pretty much identical to the aquarium pump. The modification is basically the same.
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