Emulsion is obtained when two immiscible or partially miscible liquids are shaken. Emulsions are of two types.

i) Oil dispersed in water(O/W type) and ii) Water dispersed in oil (W/O type).The O/W type on standing separate into two layers. So it is unstable. To stabilize the emulsion, a third component known as an emulsifying agent is added. The emulsifying agent helps to form an interfacial layer between suspended particles and the medium. So a stable emulsion is formed. For O/W and W/O type emulsifying agent used is gum and heavy metal salts respectively.