Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
Author: Subject: Aspirator Recomendations
ShadowWarrior4444
Hazard to Others
***




Posts: 226
Registered: 25-4-2008
Member Is Offline

Mood: Sunlight on a pure white wall.

[*] posted on 20-5-2008 at 11:05
Aspirator Recomendations


Since I've seen various posts regarding the purchase and quality aspirators, I thought it might be useful to start a thread on it.

I'll start with a request for an assessment of the quality of this aspirator (from one of my favorite companies):
http://cynmar.com/item_detail.aspx?ItemCode=VAC54137

And perhaps a useful inclusion, this vacuum gauge:
http://cynmar.com/item_detail.aspx?ItemCode=VAC54178

I have purchased from Cynmar in the past, and can attest to the quality of their merchandise, prices, and customer service.

An analogous ebay version is pricier, and seemingly less functional: Avogadro's Lab Supply




A bit of my photography (usually chemisty/physics inspired): ShadowWarrior4444.deviantart.com/gallery
View user's profile Visit user's homepage View All Posts By User
evil_lurker
International Hazard
*****




Posts: 767
Registered: 12-3-2005
Location: United States of Elbonia
Member Is Offline

Mood: On the wagon again.

[*] posted on 20-5-2008 at 11:39


Both crap. I got an aspirator from Cynmar one time and it shot more water out the side arm than it did the outlet! This is the one you want:



http://vwrlabshop.com/polypropylene-vacuum-pump-aspirator-na...

As far as gauges, if you intend to do a fractional distillation under vacuum, you need a mercury manometer... there really is no substitute. For the money, the $117 Ace Glass 8733-07 "stick" manometer can't be beat. Simply evacuate using a mechanical pump down to <1mm, open slooowly and the mercury gets sucked right up the center tube. Takes about 60-70g of mercury to fill it up IIRC. To use, start up your vacuum system, let it run for a bit, then open up the stopcock by giving it a little twist, watch the mercury in the center tube drop, when it stops read on the sides. Much much more accurate than any mechanical or electronic gauge IMO.



You also need some vacuum tubing. I've used the Tygon R-3603 with decent success. 1/4" seems to be the closest fit for most lab needs, however why the hell St. Gobain doesn't make 5/16" heavy wall is beyond me. Closest they have is 5/16" ID and 5/8" OD, which is supposedly rated for 29.9 inches of vacuum. According to them they could do a custom run for me, but I would need some folks to go in on orders, preferably whole 50 foot rolls.

[Edited on 20-5-2008 by evil_lurker]




Not all chemicals are bad. Without chemicals such as hydrogen and oxygen, for example, there would be no way to make water, a vital ingredient in beer.
View user's profile View All Posts By User
detritus
Harmless
*




Posts: 19
Registered: 27-4-2008
Member Is Offline

Mood: No Mood

[*] posted on 20-5-2008 at 17:13


hmm - maybe that water-squiring aspirator was just a bum unit. I used those metal aspirators at school and they were pretty good, easily pulled down to 50mm and often down to 25-30 after running a bit. Our setups had a long exit hose on the tail to prevent splashing, maybe it helps the vacuum too.
View user's profile View All Posts By User
zeppelin69
Harmless
*




Posts: 46
Registered: 20-2-2007
Member Is Offline

Mood: No Mood

[*] posted on 24-5-2008 at 20:06


I bought the vwr aspirator recomended in this thread and it works great, when I'm running it by itself. At first I thought it was because my pump was too weak, so I bought a 1/2 hp (1870 gph IIRC) pump from harbor frieght recomended elsewhere on this site, but I still can't get a vacuum when I run the line out of the aspirator to my condensor. This my first attempts at vacuum distillation so I am obviously clueless. Sould I just run the aspirator by itself on the 1/2 hp pump and the condensor on my weak pump? Basicaly, if someone wouldn't mind filling me in, I would like to know all the ins and outs of setting up my rig the right way. What order everything should be connected in etc. Thanks for all of the help guys, it's much appreciated.



I am one of the original members of http://www.dererumomnis.org/bbs/
View user's profile View All Posts By User
bio2
National Hazard
****




Posts: 447
Registered: 15-1-2005
Member Is Offline

Mood: No Mood

[*] posted on 24-5-2008 at 20:31


Good grief!

Check for leaks and make sure the correct end is hooked up.
View user's profile View All Posts By User
zeppelin69
Harmless
*




Posts: 46
Registered: 20-2-2007
Member Is Offline

Mood: No Mood

[*] posted on 24-5-2008 at 21:01


The aspirator is hooked up correctly, it pulls a vacuum fine when it is the only thing connected to the pump. The problem is that when I connect another line from the "exit" of the aspirator to my condensor, it stops working. Untill that is I disconnect the line from the "exit" and turn the pump off and back on. Does the aspirator have to be hooked up after the condensor? As far as I can tell I have no leaks. If it will help I can post a picture of my attempt to set everything up, tomorrow. Thanks again for all of your help.



I am one of the original members of http://www.dererumomnis.org/bbs/
View user's profile View All Posts By User
evil_lurker
International Hazard
*****




Posts: 767
Registered: 12-3-2005
Location: United States of Elbonia
Member Is Offline

Mood: On the wagon again.

[*] posted on 24-5-2008 at 23:57


You do not connect anything to the aspirator other than the vacuum line on the side of the aspirator. The long tubing on the discharge of the outlet should be around 1" or so from the surface of the water.

If you want to run a second line for coolant to the condender you must plumb it in-line before the aspirator, not after.




Not all chemicals are bad. Without chemicals such as hydrogen and oxygen, for example, there would be no way to make water, a vital ingredient in beer.
View user's profile View All Posts By User

  Go To Top