Bubbleplate (Stranger)
05-16-02 13:13
No 309316
      Vacuum Pump Survey  Bookmark   

I was dreaming about buying a Vacuum Pump. There's so many types out there, its a hard choice. Whats a decent brand that will be able to pull 25-29 Hg and will last a bit? Has to be able to handle solvents. I see the Gast Diaphragm types; then there's the Oil based ones like Edwards, Welch, Leybold, etc.
Any suggestions/experiences?
 
 
 
 
    tao
(Hive Bee / Eraser)
05-16-02 14:47
No 309338
      teflon  Bookmark   

I remember hearing about knf teflon oiless pumps. For a nice one you have to pay but it's very resistant to solvents and doesn't require a lot of maintenance.
 
 
 
 
    hest
(Hive Addict)
05-16-02 18:25
No 309421
      unit's  Bookmark   

USE A PROPER WACUM UNIT
torr mmHg and (best) mbar will work.
I guess that 25-29 Hg means 25-29 inch of Hg, that is less than a lousy watherpump. For destilation you need 1-7mbar.
(twostag oilpump's from Edwards like 2E2 is a greath pump)
 
 
 
 
    wyndowlicker
(Hive Bee)
05-16-02 23:36
No 309567
      get the  Bookmark   

get the ritchie yellowjacket 1.5cfm or 3 cfm bad ass pump its even got the shape of a bee.gets you where you want to go.tongue

I will choke untill I swallow!Who are you to judge or strike me down!Miss you Kerra!
 
 
 
 
    sYnThOmAtIc
(Hive Bee)
05-24-02 07:31
No 313464
      Distillation question  Bookmark   

Is it possible to lose goods during a vac distillation? Say one is using a 3cfm vacuum pump boils water at about 10c give or take a lil. Will the vapors of the boiling substance be evacuated in to the pump line?
 
 
 
 
    Osmium
(Stoni's sexual toy)
05-24-02 10:44
No 313531
      Yes, that is a real possibility. E.g.  Bookmark   

Yes, that is a real possibility. E.g. when you distill sassy oil at a temp of 70C quite a bit will end up in your pump. That's one reason why your distillation temperature shouldn't be too low and your cooling water as cold as possible.

I'm not fat just horizontally disproportionate.
 
 
 
 
    ClearLight
(Hive Bee)
05-24-02 18:09
No 313654
      cold trap?  Bookmark   


  sounds like a calcium chloride/water cold trap is needed... btw what are the tradeoffs between the diaphram based pumps and the oil based???

   Ever since I heard about the guy who got busted when they gc/ms his pump oil, I got reaaall leary about oil pumps..


Infinite Radiant Light - THKRA
 
 
 
 
    Osmium
(Stoni's sexual toy)
05-24-02 18:53
No 313671
      Oil pumps usually reach a lower vacuum, but of ...  Bookmark   

Oil pumps usually reach a lower vacuum, but of course are more prone to corrosion than full-teflon diaphragm pumps.

> Ever since I heard about the guy who got busted when they
> gc/ms his pump oil, I got reaaall leary about oil pumps..

They will find the same residues in a diaphragm pump too.


I'm not fat just horizontally disproportionate.
 
 
 
 
    chem_123
(Hive Bee)
05-24-02 19:14
No 313679
      sweet ass  Bookmark   

keep the info. comin' boys, SWIM's gonna aquire a pump soon, and SWIM needs to know what to look for in a pump...keep talking about the difference between the different types, and what separates the men from the boys.

Dreaming of the sweet honey smile
 
 
 
 
    pickler
(Greenhorn)
05-25-02 01:31
No 313774
      If your just startin out, a good pump to get is ...  Bookmark   

If your just startin out, a good pump to get is the yellowjacket one. They are good and you can get one at a pawn shop for about 100 bucks. Even if it only works for one synth, you can make enough to buy 50 pumps.

We'll soon find out if I'm a chemist or not!
 
 
 
 
    chem_123
(Hive Bee)
05-25-02 09:44
No 313932
      air conditioning vacuum? you mean compressor  Bookmark   

what is the air conditioner vacuum?

Dreaming of the sweet honey smile
 
 
 
 
    Rhodium
(Chief Bee)
05-25-02 10:57
No 313953
      same difference  Bookmark   

Fridge pumps, AC units - all are air pumps. Depending if you utilize the "suck-in" or "blow-out" connection you can call them either vacuum pumps or air compressors.
 
 
 
 
    placebo
(irritable and cranky)
05-25-02 15:41
No 314020
      Os, what would be your pet, money-no-object ...  Bookmark   

Os, what would be your pet, money-no-object (within reason, say US$3k) pump of choice? Least upkeep, hassles, noise, vibration, best reliability, vacuum, all-rounder?
Please supply a url.

Bored...
 
 
 
 
    Osmium
(Stoni's sexual toy)
05-26-02 01:27
No 314185
      Depends what you need it for!  Bookmark   

Depends what you need it for!
Ideally you should have both, a diaphragm and an oil pump (KNF or Vacuubrand for the diaphragm pump).

I'm not fat just horizontally disproportionate.
 
 
 
 
    foxy2
(Distinctive Doe)
05-26-02 04:22
No 314261
      fuck  Bookmark   

I could have had a NEW, approximately $3000 knf diaphram pump for like $550.  But i waited just a bit to long....

Wonder if a bee lucky bee got it, hope so.  You Euros would have loved it cause it was wired for you, I think thats why it was so cheap.frown

Those who give up essential liberties for temporary safety deserve neither liberty nor safety
 
 
 
 
    placebo
(irritable and cranky)
05-26-02 12:10
No 314378
      Well SWIM has a pump that Os already said was too ...  Bookmark   

Well SWIM has a pump that Os already said was too big (cfm) and doesn't go as low as one would like. Although it is very nice for vac filtering etc. So in a never-ending struggle to please Os. SWIM would like a pump more befitting of his manliness. Something for vac distillation of our beloved ketone and freebase amine in glass of not insignificant size, say.. 5L RBFs. Quiet, reliable, as little upkeep as possible, not waiting an hour for ultimate vacuum.

Would something like a vaccubrand MD 4C with the PC201 (http://www.vacuubrand.net/chemistry_systems/default.htm) be acceptable?

placebo... on a never-ending journey to please Os.

Bored...
 
 
 
 
    Osmium
(Stoni's sexual toy)
05-27-02 10:59
No 314691
      These pumps are very well suited for rotovaps, ...
(Rated as: excellent)
 Bookmark   

These pumps are very well suited for rotovaps, filtrations, distillations etc. The usual in use vacuum for the smaller one is about 12-15mbar, I have used that pump often for sassy distillation, rotovapping, vacuum isomerisation etc.

For ketone and product distillation I preferred an oil pump (with really old smelly oil which I never changed, another way to limit your vacuum wink). The one rated for 2mbar should work well for that purpose too.

I once witnessed a distillation attempt of sassy using a 6L flask and a MZ2C, and it was not pretty. Lots of bumping. But that wasn't the pump's fault, you either need to use a capillary extending to the bottom of the flask for good mixing or overhead stirring. Magnetic stirring didn't work. The reason is that the oil overheated at the bottom of the flask, and when it reached the surface it vigorously boiled causing the horrible bumping.

Let's say you have 15mbar of vacuum in the vapor phase above the liquid and 20cm (8 inches)of oil in the flask. Then the pressure on the flask's bottom will be much higher, meaning the oil will overheat. Using the above numbers and assuming the oil has a density of 1.0 the pressure on the bottom of the flask will be about 35mbar (because of the liquid column's weight has to be added)! Without efficient stirring this hot overheated oil, when it eventually rises to the surface will explosively evaporate. Using a capillary will make sure that the vacuum is the same everywhere, and the introduced gas bubbles will sort of catalyse the evaporation/boiling.
Same happens during the vacuum isomerisation BTW, that's why I never did it big scale. A 2L flask worked well with magnetic stirring, bigger ones were bumping horribly.

I'm not fat just horizontally disproportionate.
 
 
 
 
    Rhodium
(Chief Bee)
05-28-02 00:06
No 314917
      Why stuff bumps under vacuum  Bookmark   

Oh, so that's why stuff bumps much easier with high vacuum! I've never read that ANYWHERE - of course physical chemistry theory will make you able to predict that, but the tough part is to make the connection in the first place!

I'd like you to write a 250+ page book called "Tips & Tricks in the organic chemistry laboratory", you always seem to have so good explanations for every little practical thing one hasn't thought about before!
 
 
 
 
    Bubbleplate
(Stranger)
05-29-02 02:18
No 315364
      Thanks all for your comments and suggestions  Bookmark   

They'll be helpful when shopping. BTW, I seemed to have run across what looks to be a great deal:
http://www.XXXXXXXXXXXXXXXXXXXXXXXx
NO SOURCES!!!
Check it out.