A mixture of two immiscible liquids (such as water and oil) can be separated by using a separating funnel.

When the mixture of water and mustard oil is put in a separating funnel, it forms two layers. Water being heavier, forms the lower layer in the separating funnel whereas oil being lighter forms the upper layer. On opening the stop cock of separating funnel, the lower layer of water comes out first and collected in a beaker. When water layer has completely run off, then stop cock is closed. the oil is left behind in the separating funnel. It can be removed in a separate beaker by opening the stop cock again.