Author Topic: Sep funnels  (Read 2701 times)

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abolt

  • Guest
Sep funnels
« on: August 09, 2004, 02:10:00 AM »
Silly noober Q:

Why do Sep funnels hold more than the written amount? (e.g. - a sep funnel marked 1 litre will hold nearly 2 litres of liquid?)

Is there a rule behind this?


Osmium

  • Guest
Mine don't. I cannot get much more than 2L...
« Reply #1 on: August 09, 2004, 02:27:00 AM »
Mine don't. I cannot get much more than 2L inside the 2L sep funnels.

Maybe your 1L device is meant for extracting 1L so that's why there is extra room?
Don't complain about it, just be grateful you haven't broken it yet.


biffman

  • Guest
Gee, I never really checked.
« Reply #2 on: August 10, 2004, 09:13:00 PM »
I have 250ml, 500ml and 1 and 2 litre sep funnels but I never checked the actual volume that they contain.  I just assumed that there was an additional headspace in there for shaking and or for the volume to be extracted as Osmium mentioned.
  Maybe it is brand dependant?
  The bigger the better I find.
   The smaller one's (which are from the earlier learning days) I only use for breaking up emulsions from shaking in the larger seps.
  Here's my trick:
   Do the shaking extraction and let stuff settle for a while. If there is an emulsion or foamy layer take a coat hanger that has been straightened out and use it to rub up and down againt the sides of the flask to help break up the emulsion. Sometimes it helps a lot, sometimes not at all.  Usually you have to let it sit for a while before you get any obviously separation improvement.
  Often, after the separation of the lower layer, you will get a persistant emulsion which just seems to refuse to separate.  Here's a trick that works wonders in breaking apart that emulsion using smaller separatory funnels...
  Drain the emulsion (only tried with DCM in SWIM's experience) into another separatory funnel, but direct the flow slowly down the walls of the receiving funnel while slowly turning the receiving funnel in your hand.  Try to direct the flow onto the ground glass surface of where the stopcock would go, and as it flow into the receiving funnel it seems that as it goes down the glass surface the foam gets retained much more than the DCM and the heavier layer separates quite nicely.  Then use the little coat hanger probe again to make even a better separation.
  You can do this several times until you think you've gotten what you can. 
  Emulsions are no fun and separating them can be a bit of an art form but I found that this is a good little physical technique to shorten the wait.

I apologize for getting off topic there.
(Damn ethanol!)

Rhodium

  • Guest
Easier clearing of emulsions
« Reply #3 on: August 11, 2004, 07:21:00 AM »
Emulsions are no fun and separating them can be a bit of an art form but I found that this is a good little physical technique to shorten the wait.

Reliable emulsion clearing in two minutes:

Post 384761

(Rhodium: "CeliteRocks! [Filter Aid / Emulsion Elimination ]", Methods Discourse)



LoW_JacK

  • Guest
thats sure funny. I've sold my 500ml sep ...
« Reply #4 on: August 14, 2004, 11:03:00 PM »
thats sure funny. I've sold my 500ml sep funnel as I didnt ever use it for anything. Ghetto me promotes the use of a 2liter soda bottle for sep funnelling and if you must get a whole 2 liters funneled and seperated that way buy a 3liter soda bottle made from plastic and leave the glassware like giant sep funnels to the real chemists that evidentally can not only afford them, but have the brains and presence of mind as to not wind up breaking that $drop in the bucket funnel.

A large sep like one that you can cram 2 liters into will cost you more than $100.00, (the legal glassware limit). Therefore, unless connected like a big dog , dont bother with a glass sep funnel. (my opinion only) . Some RXN's wont let you get away with a 2 liter bottle and a sep is a must. So weigh your wallet versus your needs and settle for whatever you must have. I just always thought I needed one of them glass seps until I got one and then wanted to kick myself in the ass for not getting one with a quality stopcock.  Ground glass stopcocks are cheaper, and cheaper is never better in glassware. Unless your talking earlenmeyers , then cheap is alright and sought. Stopcocks are expensive even if your getting one without the sep funnel. Teflon stopcocks are the shit and their cost is a reflection of their quality. JUST SAY NO TO GROUND GLASS STOPCOCKS!

My 1 1/2 cents


Jacked

  • Guest
shit
« Reply #5 on: August 21, 2004, 12:29:00 PM »
Shit I use to sleep with my 2L sept funnel, I thought they were delivered from heaven. My wife even has a pair of ear rings that are about .25 ml sept funnels that actually work...