It is a colloidal system existing of the dispersed phase and a dispersion medium in a liquid state. When we add drops of oil in water and mix it properly globules of oil are dispersed in dispersion medium water, generally, globules are of 10 -6 m in size. Example of the natural emulsion is milk.

On the basis of the dispersed phase and dispersion medium, there are oil in water (O/W) emulsions and water in oil emulsion (W/O). In O/W emulsion oil is dispersed phase and water is dispersion medium or continuous phase, a common example is milk and vanishing cream etc. In W/O emulsion water is dispersed phase and oil is dispersion medium example include cold cream and cod liver oil etc.

The emulsions are prepared by mixing both phases together at high speed by use of stirrers like magnetic stirrer, mechanical stirrer or by ultrasonic vibrators. There is the use of different emulsifiers or stabilizers to reduce the surface tension between the dispersed phase and dispersion medium and to prevent them from separating out. Emulsifiers can be water soluble or oil soluble added into the component in which they are soluble first and mixed with another component. Examples include gelatin, sodium oleate, and magnesium oleate etc.

Emulsions have the property of zig-zag motion i.e. Brownian movement, they show phenomena of Tyndall effect and they also get influenced by electric current as they have the property of electrophoresis. The particles of the dispersed phase are in 1000 A° to 10000 A°. On addition of electrolytes, coagulation occurs which is indicative of a negative charge on globules.

To identify emulsions there are various tests like dilution test i.e. if emulsion gets diluted with water it is an O/W emulsion and if not, it is a W/O emulsion. Dye test involves the use of water and oil soluble dyes. Under the microscope if water-soluble dye is used and if background comes out to be colored it is O/W emulsion. Conductivity test, if conductivity property is there then it is O/W emulsion if not then W/O.

To separate the two components i.e. oil and water demulsification process are performed by heating, centrifuging and freezing.

Emulsions have its applications in food industry i.e. milk and dairy industry by stabilizing the products with natural surfactants. In pharmaceuticals for dispensing insoluble drugs. Emulsions also have application in agriculture as formulations for treating plants.

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