What is an Emulsion?

An emulsion is a colloidal solution in which the dispersed phase, and a dispersion medium, are both liquids. As emulsion is a colloid, its particle size is between the true solution and suspension.

Colloidal System: The heterogeneous mixture with particle size in the dissolved state is between \({\rm{1 nm}}\) to \({\rm{1000}}\,{\rm{nm}}\) is called a colloidal system. A colloidal solution always consists of at least \(2\) phases that are dispersed phase and the dispersion medium.

Dispersed Phase: It is the component present in small proportion and consists of particles of colloidal dimension.

Dispersion Medium: The medium in which colloidal particles are dispersed is called a colloidal medium.

Types of Colloidal System

What are the 2 Types of Emulsion?

The emulsion is broadly classified into two types:

1. Oil in water (O/W type) emulsions: In this type of emulsion, oil acts as a dispersed phase, and water acts as the dispersion medium. Example: Milk, Vanishing cream, etc.
2. Water in oil (W/O type) emulsions: In this type of emulsions, water acts as a dispersed phase, and oil acts as the dispersion medium. Example: Cold cream, butter, cod liver oil, etc.

The two types of emulsion can be interconverted simply by changing the proportion of the dispersed phase and dispersed medium.

How to Distinguish W/O and O/W Emulsion?

The following tests are used to distinguish W/O and O/W emulsion:

1. Dye Test: To the emulsion, some oil-soluble dye was added. If the background becomes coloured, the emulsion is water in oil type, and if the droplets become coloured, the emulsion is oil in water type.
2. Dilution Test: If the emulsion can be diluted with water, this indicates that water is the dispersion medium and the emulsion is of oil in water type. In case the added water forms a separate layer, the emulsion is water in oil type.
3. Conductance Measurement: In this method, a small amount of electrolyte is added to the emulsion, and a change in its electrical conductance is observed. If there is an increase in conductance, the emulsion is oil in water. If there is no significant change in conductance, it is water in oil emulsion.

Characteristics of Emulsions

1. Emulsion exhibit the Tyndall effect, Brownian movement, electrophoresis, etc. Tyndall effect: The scattering of the light by the colloidal particles in a colloidal solution is called the Tyndall effect.

Brownian movement: It is the continuous zig-zag movement of the colloidal particles in a colloidal solution.

Electrophoresis: It is the movement of colloidal particles under the influence of an electric field.

2. The droplets in the emulsion are generally negatively charged.
3. They can be coagulated by the addition of electrolytes containing polyvalent metal ions.
4. Emulsions can be diluted by adding any amount of dispersion medium. However, the addition of the dispersed phase results in the formation of separate layers.
5. Emulsions can be broken into separate liquids by heating,zing, centrifuging, electrostatic precipitation by adding a large amount of the electrolytes to precipitate out the disperse phase or by chemical destruction of the emulsifying agent.

How to Prepare an Emulsion?

The process of making an emulsion is known as emulsification. Emulsions may be obtained by vigorously agitating a mixture of both liquids. But this creates an unstable emulsion that disperses drops at once, comes together, and forms a separate layer. Emulsifying agents or emulsifiers are added to stabilize an emulsion. These form an interfacial film between suspended particles and the dispersion medium.

The substances added to stabilize the emulsion are called emulsifying agents. The emulsifying agent for W/O type emulsions is heavy metal salts of fatty acids, long-chain alcohols, lampblack, etc. The emulsifying agent for O/W type emulsions are proteins, gums, natural and synthetic soaps, etc.

Demulsification: The decomposition of an emulsion into its constituent liquids is called demulsification.

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Applications of Emulsion in Real Life

1. The cleansing action of soap: Washing action of soap is due to grease emulsification and taking it away in the water along with dirt or dust present on grease.

2. In medicines: A wide variety of pharmaceutical preparations are emulsions. Example: Emulsion of Cod liver oil.

3. Digestion of fats: Digestion of fats in the intestines is added by emulsifications. A little of the fat forms a sodium soap with the alkaline solution in the intestine, and this soap emulsifies the rest of the fat.

4. In disinfectants: The disinfectants such as Dettol and Lysol give emulsions of the oil in water type when mixed with water.

5. In metallurgical operations: Emulsions play an important role in the industry. The metal ores are concentrated by the froth floatation process, which involves the treatment of the pulverized ore in the emulsion of pine oil.

6. In building roads: An emulsion of asphalt and water is used for building roads.

Summary

An emulsion is a colloidal solution in which the dispersed phase, and a dispersion medium, are both liquids. As emulsion is a colloid, its particle size is between the true solution and suspension. In this article, you have grasped an idea about the type of colloid, i.e., emulsion, its types, preparation, properties, etc. This knowledge will also help in understanding other types of colloids such as aerosol, sol, gel, etc. You also learnt the characteristics and real-life applications of emulsions along with some frequently asked questions.

PRACTICE QUESTIONS RELATED TO EMULSION

Frequently Asked Questions (FAQs) on Emulsions

1. What are the 2 types of emulsion?
Answer: Two types of emulsion are Oil in water (O/W) and Water in oil (W/O).

2. How do you define emulsion?
Answer: The emulsion is a colloidal solution in which the dispersed phase, as well as a dispersion medium, are both liquids.

3. What are examples of emulsion?
Answer: Few examples of emulsion are milk, hair cream, butter, cod liver oil, etc.

4. Is milk an example of emulsion?
Answer: Yes, milk is an emulsion because, in milk, both dispersed phases, i.e. fat and dispersed medium, i.e., water is liquid.

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