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Keras
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Vacuum aspirator using DMSO
According to the Gaylord corp's technical bulletin, DMSO has a rt vapour pressure of circa .5 mm Hg, or around 70 Pa, vs 3.2 kPa for water.
Did anyone ever attempt to pull a vacuum using DMSO and an aspirator?
[Edited on 25-6-2019 by Keras]
Attachment: DMSOVapPress.pdf (271kB)
This file has been downloaded 341 times
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Pumukli
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I had the same (very similar) idea months ago: why not use ethylene-glycole in a recirculating aspirator system?
Glycol is fairly cheap and has much lower vapour pressure than water (at least it should have, I didn't bothered to check).
Problems I see:
- price of the working fluid (DMSO is not that cheap)
- if it absorbs water then the achievable vacuum will eventually deteriorate
- these fluids has much higher viscosity than water, it may cause problems with the pump
Anyway, my feeling is if it worked we already had seen completed projects, working units in commerce. Do you know such system? I don't. So there's
obviously a stumbling block somewhere what we don't see yet.
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Keras
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I agree for the viscosity. In fact, just after the graph plotting partial pressure vs temperature, there's a viscosity graph, too. But I have no idea
how viscosity units translate into the real world, i.e. what is viscous vs. what is not.
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Tsjerk
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Fractionated diesel fuel?
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walruslover69
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diesel and Kerosene would probably make good candidates due to their relatively low viscosity. I think you will definitely need a efficient solvent
trap to prevent whatever you are pumping off from mixing with the working fluid. I imagine DMSO could also be very hard or incompatible with the seals
on common pumps.
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Sulaiman
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Vacuum pump oil ?
CAUTION : Hobby Chemist, not Professional or even Amateur
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DavidJR
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DMSO sounds like a great way to end up with a big vat of contact poison
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Keras
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DMSO is not that toxic, is it?
I agree kerosene could be a better idea, but it is flammable…
[Edited on 25-6-2019 by Keras]
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Metacelsus
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No; in fact I regularly use 10% DMSO as a cryopreservative for cells, which handle it just fine.
However, DMSO solutions, along with any solutes, are easily absorbed by skin contact. So if anything toxic is dissolved, it would be dangerous.
[Edited on 2019-6-25 by Metacelsus]
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Ubya
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Quote: Originally posted by walruslover69  | | diesel and Kerosene would probably make good candidates due to their relatively low viscosity. I think you will definitely need a efficient
solvent trap to prevent whatever you are pumping off from mixing with the working fluid. I imagine DMSO could also be very hard or
incompatible with the seals on common pumps. |
If you need to use a cold trap why the hassle of using a water pump? HVAC rotary vane vacuum pumps can be bought now for less than $60 on Ebay, and to
use them you need a trap. The point of using a water aspirator (in my opinion) is to not have to worry about a trap, at the end if the water is too
contaminated, just change it, it's not as expensive as a vacuum oil change.
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RedDwarf
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Ignoring all the hassle of using DMSO, just assuming you'd need a minimum of a couple of liters of dmso to fill the system I really can't see how it'd
be less expensive than buying a vacuum pump.
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SWIM
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I like the vacuum pump oil suggestion, but there's always Lucas DOT 4 brake fluid too.
Vapor pressure 10 Pa, boiling point 232 C. 121 C flashpoint.
But if you're really after low pressure and damn the consequences, how a bout a garbage can full of mercury?
(hope you've got a strong floor)
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happyfooddance
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For all the emphasis I see on scimad (and elsewhere) regarding ultimate vacuum, I would hope to see even more focus on preventing and eliminating
vacuum leaks.
Because anyone who understands knows this is where true battle lies
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Keras
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BTW do you have any idea of the vacuum that a common, run-of-the-mill vacuum cleaner can pull?
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happyfooddance
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Just a few inches of mercury
They move a lot of air though
[Edited on 6-26-2019 by happyfooddance]
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Sulaiman
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about 1/5 th pressure reduction, -20kPa relative to atmospheric, +80kPa absolute.
O.K. for vacuum assisted filtration but probably not much else in the lab other than its intended purpose..
A £10 dc motor vacuum pump pulls about -80 kPa (20kPa abs.)
A £40 HVAC vacuum pump can achieve about 10 Pa abs.
My £85 dual-stage rotary gets down to below 1 Pa ... if you believe the specs.
Peristaltic pumps, hand-operated (brake bleed) vacuum pumps etc. are also viable options.
If you have mercury then a Sprengel pump may be viable
(Cody's Lab has a video on YT)
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Keras
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The reason I was asking is that I bought those space saving bags you can put duvets into. Once it’s done, you suck the air out using a simple vacuum cleaner and you get something not only
pretty squeezed (packed up, takes less space), but also that looks as if there’s hardly any air left inside.
[Edited on 26-6-2019 by Keras]
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Ubya
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| Quote: Originally posted by Keras | The reason I was asking is that I bought those space saving bags you can put duvets into. Once it’s done, you suck the air out using a simple vacuum cleaner and you get something not only
pretty squeezed (packed up, takes less space), but also that looks as if there’s hardly any air left inside.
[Edited on 26-6-2019 by Keras] |
you could do it even by sucking air with your mouth (on a small bagbif you don't want to get light headed). 1 atm = 14 psi, so even if you can create
a vacuum of half a atmosphere every squared inch of those bags feels a weight of 7 pounds, you can see why the get so flat 
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happyfooddance
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What Ubya said.
You can pull a better vacuum with your lungs (I've been doing it with ziplocks of cheese for damn near 30 yrs).
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Sulaiman
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sucking 'cheese-air' sounds ok ... sucking 'duvet-air' sounds less appealing
(mites and their shit etc.)
one thing to be aware of with vacuum storage bags,
they are not hermetically sealed, air slowly leaks in,
then the contents try to resume their natural volume.
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happyfooddance
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Also, what Sulaiman said
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Keras
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Hah. I remember bringing back munster from Alsace. It'd better be carried in a vacuum pack, because otherwise I would've been kicked out of the
carriage!
Ok, thanks for all your answers! 
[Edited on 27-6-2019 by Keras]
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Fyndium
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https://www.ebay.com/itm/220V-Portable-Double-Stage-Rotary-v...
Are these of any good?
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monolithic
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Not sure what country you're in but for that amount of money you might able able to find a used lab grade pump which typically pull a better vacuum
and have longer duty cycles and lifetimes than Chinese HVAC pumps. https://www.ebay.com/itm/SAVANT-VP-100-VP100-TWO-STAGE-HIGH-...
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Sulaiman
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A dual/double stage rotary vacuum pump is nice to have (I have one)
but a single stage is adequate for chemistry use
and can be cheap enough to risk a little damage,
unlike my dual stage rotary which I rarely use due to fear of damage.
CAUTION : Hobby Chemist, not Professional or even Amateur
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