The third substance or agent which produce the film between the interface of two immiscible liquids and thus stabilize the system are known as an emulsifying agent.
Since the solubility of the liquids depends on the polarity of the mixing liquids the thumb rule of solubility is like dissolves like that means polar liquid dissolves in polar liquid only and vice versa. For two immiscible liquids, the emulsifying agent is used which does not chemically change the polarity of liquids but acts as bridge between immiscible liquids, the polar end of the emulsifier attach to the polar liquid and the non-polar end of the emulsifier attach to the non-polar end and thus help in dissolving.
Therefore, the one end of the emulsifier is polar and the other end is non-polar
