With a stopper at top, and a stopcock (tap) at the bottom, a separatory funnel is used to separate liquids of different specific gravities. This example came from Brown University.
Ref: A. & C. R. Aikin, <i>A Dictionary of Chemistry and Mineralogy</i> (London, 1807, vol. 2, p. 522, and plate 2.
John Joseph Griffin, <i>Chemical Handicraft</i> (London, 1866), pp. 171-174.