To use a separating funnel, the two phases and the mixture to be separated in solution are added through the top with the stopcock at the bottom closed. The funnel is then closed and shaken gently by inverting the funnel multiple times; if the two solutions are mixed together too vigorously emulsions will form.

Why is it important to vent a separation funnel upside down?

Pressure may build up inside the separatory funnel when solutions are mixed, so immediately after swirling, and with the funnel still inverted, "vent" the funnel by briefly opening the stopcock to allow for a release of pressure (Figure 4.26c).

What is the purpose of the separating funnel?

A separatory funnel (sep funnel) is used to separate immiscible liquids. When two immiscible liquids are placed in a separatory funnel, two layers are seen. The denser solvent will be the bottom layer.