[Chemistry Class Notes] on Applications Colloid Pdf for Exam

Colloids are also called colloidal solutions or even colloidal systems. They are mixtures wherein microscopically dispersed insoluble particles of one particular substance are suspended in the other. The size of these suspended particles in colloids tends to range from 1 to 1000 nm. A mixture is classified as a colloid only when the suspended particles in it do not settle at the bottom of the container when they are left undisturbed. 

Colloidal solutions tend to exhibit the Tyndall effect, wherein a beam of leam that is incident on colloids tends to scatter because of the interaction occurring between the light and colloidal particles. Today, we will learn about the examples of colloids, application of colloids in food and medicine, the protective action of colloids and the different uses of colloids in different industries. Let us first take a look at some of the examples of colloids. 

Examples of Colloids

1) Blood

Blood is a respiratory pigment that contains the protein albumin in water. The pigment part consists of albumin which acts as a dispersed phase in the dispersion medium, which is water. This is a hydrosol.

2) Cloud

Clouds consist of air that is a dispersion medium and the droplets of water act as a dispersed phase. They are aerosols. 

3) Gold Sol

Gold sol is a metallic sol wherein the gold particles are dispersed in water. The food products that we eat in our day to day lives are all colloids. For example, dairy products, fruit juices, cake, bread, butter, cream, milk, whipped cream, etc. are all colloidal. 

The natural phenomena occurring around us like clouds, fog, mist, rain, etc. are colloids as well but in different forms. Dust and smoke and colloidal nature too.

The blue colour of the sky is due to the suspended dust and water particles in the air that tends to scatter blue light more than any other light. Similarly, the seawater seems blue in colour due to the colloidal matter present in it that scatters the blue light.

Fertile soil consists of colloids as well in the form of humus and clay which plays an essential role for storing and exchanging minerals.

Application of Colloids

Let us now learn about the application of colloids in food and medicine.

Colloids are used widely in several different industries and have domestic and medical applications.

1. Food Items: Day to day food items like soup, syrup, dairy products, etc.

2. Medicine: Colloidal silver named Arygyrols which acts as an antiseptic for several eye infections.

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Let us take a look at some of the other applications of colloidal dispersion.

1. Purification of Air Via Cottrell Precipitator

The process of purification of air via Cottrell precipitator consists of coagulation of the solution particles. Smoke is dust that is allowed to pass through the electrified chamber inlet that has a centralised electrical plate. This is provided with an opposite charge of the smoke particles. When dust is allowed to pass, these particles tend to coagulate and purified air passes through the other outlet.

2. Leather Tanning

Animal skin is quite soft and when it is immersed in the tannin solution having an opposite charge to that of the animal skin, particles tend to get coagulated. In turn, skin tends to become harder and the process is called tanning of leather.

3. Delta Formation

Delta formation consists of coagulation of the river particles with the help of the seawater electrolyte.

Protective Action of Colloids

The protective action of different colloids is to be compared regarding the gold number.

A lyophobic colloid is protected from the coagulation when a protective lyophilic colloid is used. The protection power is expressed in regards to the gold number, which determines the amount of protective colloid in milligrams which is required for preventing the coagulation of a 10mL standard gold sol when 1mL 10% NaCl solution gets added to it. The smaller the gold number is, the higher the protection power would be.