Q: Why will my separatory funnel not drain?
A: You must remove the stopper so the pressure inside can equalize.
Another possible reason is that stopcock grease is plugging the hole (this applies to glass stopcocks only - we don't use grease on the Teflon stopcocks). If you believe the hole is plugged, let your instructor know.

Q: Why does my separatory funnel leak?
A: If it is a funnel with a Teflon (white) stopcock plug, you should tighten the nut holding the plug in. It should be as tight as it can be without making it too difficult to turn the plug.
In the case of a glass plug, the cause is likely to be that the grease needs to be replenished, as it must from time to time. You can detect this in advance of using the funnel by examining for "streaking" of the grease in the middle section of the plug. You instructor can show you how to remove the old grease and apply new.

Q: What should I do if the iron ring is too large to hold my separatory funnel?
A: A good solution is to place a few concentric rings from the top of a steam cone on the iron ring.

Q: Does the funnel have to be dry?
A: Never. This is one piece of glassware that never needs to be dried, as one of the layers is always aqueous.

Q: How long do I have to wait until draining the funnel.
A: Just until the layers are clearly separated.

Q: My layers won't separate. What can I do?
A: You have an emulsion, and there are a few tricks you can use. The best approach is to add sodium chloride to the aqueous layer to increase the ionic strength. Sodium chloride dissolves in water to the extent of about 36g/100 mL. Estimate from your volume how much NaCl could dissolve and use half this amount. Add the solid using a wide-stem funnel (to keep the salt from sticking in the ground glass joint). Then shake until all the solid dissolves.

Q: How can I be sure which layer is which?
A: Do a solubility test. Place about 1-2 mL of water in a test tube and add a few drops of one of the layers using a disposable pipet. If it doesn't mix it's the organic layer.

©2001,2002 Daniel A. Straus