What is the primary function of a separatory funnel in laboratory operations?

The primary function of a separatory funnel in laboratory operations is to separate immiscible liquids based on their densities. This apparatus is specifically designed to take advantage of the differences in density between two liquids that do not mix well, such as an organic solvent and water. When the mixture is added to the separatory funnel, it allows for the distinct phases to form, with the denser liquid settling at the bottom. By opening the stopcock, the denser liquid can be drained off, leaving the lighter liquid in the funnel. This technique is widely used in organic chemistry for liquid-liquid extractions, facilitating the purification and isolation of compounds from mixtures without the need for evaporation or distillation, which could lead to loss or alteration of the compounds.