Rando22
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Vacuum Filtration
I have a question about Vacuum Filtration, do I need a special kind of vacuum pump, I see some are going for about $400 vs $120
Would something like this do the same job?
http://www.walmart.com/ip/Vacuum-Pump-2-Stage-3.9-CFM-1-3HP-...
What is the main difference about these expensive ones vs the inexpensive ones
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arkoma
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Link
^^ Just an example, but it's $6.25USD. Water aspirator for draining a water bed, attaches to your kitchen sink and will pull fair vacuum. The little
hand held squeeze types they sell for stuff like brake bleeding also work. Unless you have a buchner funnel the size of a 5 gallon bucket can't see
why you'd need that monster electric pump.
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Rando22
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Yes sorry I forgot to mention, I am using a buchner funnel
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arkoma
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the product you were looking at is for A/C work, which requires a deep prolonged vacuum pulled on it after replacing parts in order to remove moisture
from the system.
This is mostly sufficient: 
"We believe the knowledge and cultural heritage of mankind should be accessible to all people around the world, regardless of their wealth, social
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Rando22
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Yeah I really dont want a hand one, I have a lot of material to filter. So I cant use an HVAC one?
Edit: Is the hand one just like you build pressure up and then release it to filter?
[Edited on 17-7-2014 by Rando22]
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Magpie
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I have a vacuum pump like that only it's rated for 2.5cfm. But I only use it for vacuum distillations where it pulls down to 2 mmHg.
For Buchner filtrations I use a water driven aspirator ($15).
Up to this point my vacuum distillations have been for esters and organic acids which I judged would likely not require a condensation trap to
protect the pump from harmful vapors. When the oil starts to look contaminated (there's a window to show oil level in the sump) I change out the oil,
which I've done twice now in about 2 years.
If distilling nitric acid or other such nasties I use my aspirator. I haven't used a cold trap yet but might in the future. Setting up a trap with
solid CO2/acetone looks like a PITA.
The main difference between these cheap Chinese pumps and ones you can pay thousands of dollars for are, IMO:
1. High precision parts and 2-stage to get really high vacuum. But when would I (or other chemist) need a vacuum better than 2 mmHg?
2. More corrosion resistant materials.
3. Made in USA or Germany vs made in China.
4. Wetted parts made of ptfe so no cold trap needed.
5. Designed for general laboratory use vs air-conditioner service.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Rando22
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Hi Magipie thanks for the insights, your water driven aspirator, is that one of those ones you hook up to a sink, could you give me a link to where
you bought it so I can take a look?
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Magpie
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Yes, it is attached to my sink. It has 3/8" NPT male threads so most people would have to get an adapter to fit the regular fine threads on a kitchen
sink. I bought it from Carolina Biological about 10 years ago. It's made of nickel coated brass. I've shown pictures of it and my homemade adapter
on this site.
Nalgene makes a plastic one which many people like also.
[Edited on 17-7-2014 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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arkoma
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Rando, the thread linked to below has some good insight on aspirators. But like I said before--water bed drainers work well for
pulling enough vacuum for filtration, at least they have in my personal experience using a buchner on a suction flask. They are water aspirators.
Bear in mind the colder the water, the more ultimate vacuum they pull. Has to do with vapor pressure of water somehow.....
http://www.sciencemadness.org/talk/viewthread.php?tid=437
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Ascaridole
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Hey random22, you need an aspirator? I got a few left from when my company went to KNF pumps. U2U me if your in the US and I'll send it to you.
[Edited on 17-7-2014 by Ascaridole]
Ascaridole, the masked bandit of chemistry!
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arkoma
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Quote: Originally posted by Ascaridole  | Hey random22, you need an aspirator? I got a few left from when my company went to KNF pumps. U2U me if your in the US and I'll send it to you.
[Edited on 17-7-2014 by Ascaridole] |
This forum is awesome
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Ascaridole
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Perhaps a thread of "free" equipment for the beginner is in order?
Ascaridole, the masked bandit of chemistry!
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arkoma
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I've been BLESSED three times now via u2u's....................I've posted about it but in whimsy-yer a few posts away from access there.
Got an awesome box of "essentials" today for free--ring stand, sep and buchner funnels, etc. Someone I've NEVER met in person. Luv this place.
"We believe the knowledge and cultural heritage of mankind should be accessible to all people around the world, regardless of their wealth, social
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Rando22
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Wow awesome! Thanks guys, appreciate it!
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