Sciencemadness Discussion Board

Separatory funnel

vulture - 28-2-2003 at 09:43

I've got a rather annoying problem with my separatory funnel. When I filled it with acetone the valve leaked a few drops but that stopped very quickly.
When I wanted to drain off some acetone I noticed the valve got stuck. There is no way to turn it.

Anybody got a nifty suggestion?

madscientist - 28-2-2003 at 10:14

I've had the valve of my separatory funnel get stuck before, and I found that I can free it by pushing the rotating knob sideways (instead of trying desperately to rotate it).

vulture - 15-3-2003 at 13:17

Well, that didn't work.
The lab head at my university suggested carefully heating it above a bunsenburner, that's what they always do.

CherrieBaby - 2-4-2005 at 23:36

You have to heat the funnel but not the tap. In practice you can't do that but you should be able to have the funnel get more heat than the tap.

They sometimes suggest putting it under a hot water tap.

Darkblade48 - 2-4-2005 at 23:46

Errr, wasn't this thread like 2 years old? I think vulture would have figured it out by now ;)

But I did learn that you could use a bunsen burner flame to undo stuck valves :D

sep funnell

aldol - 3-4-2005 at 01:28

instead of using it dry you should be taking the tap out each time cleaning it and coating it with tefflon . or vasaline
make shaw you dont coat it in line with the holes . above or below the holes !
This will stop your leaks as well

CherrieBaby - 8-4-2005 at 10:39

The other thing you can do is spray it with WD 40 and leave it for 10 minutes then try again.

mick - 9-4-2005 at 09:17

It has probably been mentioned before but a quick summary.

Glass on glass can some times be shifted with heat unless contaminated with alkali and then low heat just seems to fuses them together.
Annelling temperature might work.
PTFE on glass is temperature sensitive. The expansion coefficients are different. PTFE can seize in a glass barrel over 40-50oC temperature rise unless checked or will become loose at low temperatures.
A top quality glass tap with a smidging of the right lubricant should work. Silcone OK for water, paraffin wax is OK for nBuLi in hexane because there is no real contamination but it needs topping up.
Wet and dry sanding paper with WD40 can be used to lap a glass tap in.


sep funnell

aldol - 9-4-2005 at 18:09

you could take it to a glass blower and they will fit a hole new tap fairly cheap .
depending on what the funnell is worth
also they will proberly ask you what has been in it .
personly i would not use a sep funnell with a glass tap mine has a teflon tap they are great .
mine has also had a new tap fitted
but i have a freind that worked at a uni for thirty years as a glass blower .
a genius to watch
regards aldol