Write a note on emulsion.Discuss types, properties and use of emulsion.

Anemulsionis acolloidof two or moreimmiscibleliquidswhere one liquid contains a dispersion of the other liquids. In other words, an emulsion is a specialtype of mixturemade by combining two liquids that normally don't mix. The word emulsion comes from the Latin word meaning "to milk" (milk is one example of an emulsion of fat and water). The process of turning a liquid mixture into an emulsion is calledemulsification

Properties of Emulsions

Emulsions usually appear cloudy or white because light is scattered off the phase interphases between the components in the mixture. If all of the light is scattered equally, the emulsion will appear white. Dilute emulsions may appear slightly blue because low wavelength light is scattered more. This is calledthe Tyndall effect. It's commonly seen in skim milk. If the particle size of the droplets is less than 100 nm (a microemulsion or nanoemulsion), it's possible for the mixture to be translucent.

Because emulsions are liquids, they don't have a static internal structure. Droplets are distributed more or less evenly throughout a liquid matrix called the dispersion medium. Two liquids can form different types of emulsions. For example, oil and water can form an oil in water emulsion, where the oil droplets are dispersed in water, or they can form a water in oil emulsion, with water dispersed in oil. Further, they can form multiple emulsions, such as water in oil in water.

Most emulsions are unstable, with components that won't mix on their own or remain suspended indefinitely.

Examples of Emulsions

Oil and water mixtures are emulsions when shaken together. The oil will form drops and disperse throughout the water.
Egg yolk is an emulsion containing the emulsifying agent lecithin.
Crema on espresso is an emulsion consisting of water and coffee oil.
Butter is an emulsion of water in fat.
Mayonnaise is an oil in water emulsion that is stabilized by the lecithin in egg yolk.
The photosensitive side of photographic film is coated with an emulsion of silver halide in gelatin