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Dr.Bob
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Take a simple needle valve and put in into the system with a T valve, preferably after any traps and vacuum gauge. Then you can leak a small amount
of air into the system to lower the vacuum as needed. We used to that often for vac. distillations of lower boiling things, so that they could be
condensed back without needing dry ice. That also helps dilute whatever stuff gets past the traps. If you let air in before the trap, it makes it
work less well, as the air warms your ice and also blows through the trap, helping to volatilize what is in it.
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Burner
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BTW, you may want to consider one of these (http://www.ebay.com/itm/Brinkmann-B-169-Vacuum-Aspirator-gub...). I have one and I just load it with some water and ice and it works like a charm
for many applications. Also, this particular one is starting off at a truly excellent price (59USD). I have not seen any below ~125USD as a starting
price (not that I have been looking closely). These usually seel for >300USD.
Now, if you are looking for the "fancy" approach, you can get one of these (http://www.ebay.com/itm/ISS-Enprotech-Uniequip-Refrigerated-...) that has a built-in refrigeration unit and full temperature control! 
[Edited on 8-5-2014 by Burner]
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Haber
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@Burner
How much vacuum can those pull?
Would you be able to distill high boiling solvents with that?
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Burner
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^^^ They are normal water aspirators, so you can expect similar performance. Using an ice bath on my Brinckman system I routinely achieve 7-9 mmHg.
Using the refrigerated version that I linked above I suspect that ~5 mmHg and below would be possible using a water/glycol system for the aspirator
and cooling temperatures below 0C.
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macckone
Dispenser of practical lab wisdom
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20mbar (15mmHg) is the rating on the brinkmann.
http://www.labsupplyoutlaws.com/brinkmann-recirculating-wate...
Using a glycol or salt solution or cooling would significantly lower that.
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nannah
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Hi i have been thinking about making a recirculating aspirator, but i dont know what kind of water pump thats needed. I have a pretty powerful
immersible aquarium pump that pump 1050 liters/hrs and shoot up water up to 2 meters. Do you think i could i use it so i dont have to get a new one?
I also found diaphragm pumps that were pretty cheap. But the ones i saw were all less powerful then the one i already have.
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cristall
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On labx, I found a PTFE pump that varies pressure for $140. Wow right??
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zed
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http://www.harborfreight.com/3-cfm-two-stage-vacuum-pump-608...
Bought one of these recently. I know it has limitations, but it's pretty nifty. I'm gonna break-down and use traps with it. Will it last forever?
No. But, it is good enough for what I'm going to use it for.
Rumor has it, these models spray out a little oil. Well, oil is cheap. Also, the guts may not have good corrosion resistance...... So, change the
oil often and use traps. Should do that anyway.
I walked out he door with a new one, for just about a hundred bucks. Had a 25% off coupon.
"Comments about Pittsburgh Automotive 3 CFM Two Stage Vacuum Pump:"
"Used to work on the car and to evacuate a mini split AC. Specs says it pulls down to 22.5 micron but when I put the lab spec cpm digital vacuum meter
on it deadhead it pulled to 8 microns. ( far better than the hoses most have) That is really good for a less than $200 device. At 3cfm, it is not fast
but mine seems to be well designed and exceeded the specification by a wide margin."
[Edited on 12-5-2015 by zed]
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vmelkon
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Quote: Originally posted by peach  | Thats nothing, i was distilling 12 pounds of potassium under pressure using a couple of old beer bottles and an oxy actelyene torch. It was taking
awhile so i moved the setup next to the spa bath and sat there naked when the whole shebang fell into the spa wit me!! Tell you what potassium at
1000C doesn't get along with water very well and luckily i had my resist injury key on otherwise i would have been toast.
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Beer bottles? I hope they were made of steel and not glass.
Usually, when someone says beer bottle I think of those brown glass bottle with a flute neck.
[Edited on 12-5-2015 by vmelkon]
Signature ==== Is this my youtube page? https://www.youtube.com/watch?v=tA5PYtul5aU
We must attach the electrodes of knowledge to the nipples of ignorance and give a few good jolts.
Yes my evolutionary friends. We are all homos here. |
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Mush
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| Quote: Originally posted by nannah | Hi i have been thinking about making a recirculating aspirator, but i dont know what kind of water pump thats needed. I have a pretty powerful
immersible aquarium pump that pump 1050 liters/hrs and shoot up water up to 2 meters. Do you think i could i use it so i dont have to get a new one?
I also found diaphragm pumps that were pretty cheap. But the ones i saw were all less powerful then the one i already have. |
NurdRage
Lab Equipment: Aspirator Vacuum Pump
https://www.youtube.com/watch?v=tYLlkTDstmo
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Mush
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People get low pressure with Faucet Aspirator/Vacuum Pump, because the water flow rate of these little pumps (example: 12V 130PSI & 6L/Min High
Pressure Diaphragm Self Priming Water Pump ) mostly in 6-8l range.
https://www.coleparmer.co.uk/i/thermo-scientific-6140-0010-f...
The above aspirator has a Max Flow Rate of 11.5 Liters/min. If one can find either a higher flow rate pump or lower flow rate aspirator than the
theoretical max vacuum can be achieved imo.
This kit looks nice:
Nuotrilin 40W DC 12V 24v food grade liquid pump Diaphragm Water Pump Self-priming 12L/min big flow US $33.47+ US $18.83 shipping
https://www.aliexpress.com/item/33002393098.html?spm=a2g0o.p...
[Edited on 5-12-2019 by Mush]
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