Separatory Funnel: Filling and Mixing

Familiarize yourself with the operation of the valve at the bottom of the separatory funnel. Note that the valve is off when the handle is perpendicular to the stem of the funnel. Be sure the valve is in the off position before attempting to fill the funnel.

Remove the stopper from the funnel and add the sample mixture and extracting solvent using a funnel.

After adding the two liquids you should observe two distinct layers in the separatory funnel. In the figure at right note that the upper layer initially contains the purple dye. Our goal is to extract this dye and deposit it in the lower layer.

Reinsert the ground glass stopper and hold it between two fingers.

In the following steps you will be inverting the separatory funnel. To avoid leaks or worse still, the stopper falling out, use two fingers (figure at right), to hold the stopper in place.

Invert the separatory funnel and mix the contents.

Remember to hold the stopper firmly! Mixing can be accomplished by swirling or shaking the contents of the funnel. Since our goal is bring the two solvents in intimate contact with one another, shaking is best. However, when the two solvents are known to form emulsions (when one solvent breaks up into microdroplets suspended in the other solvent), the separatory funnel should be gently swirled.

Point the inverted separatory funnel away from others and frequently open the valve to reduce built up pressure.

The released gas sometimes carries with it a small amount of solvent. Therefore, first aim the funnel straight up so that it is pointing away from you and anyone else in the lab. Now open the valve momentarily. You may hear a slight fzzzt sound as the gas is released. Vent the funnel frequently as you swirl or shake the solvent mixture.

When the extraction is complete, return the separatory funnel to the ring stand and prepare to drain the contents.

In the illustration at right notice that most of the dye is now dissolved in the lower solvent although a trace amount of dye still exists in the upper solvent.