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.
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.
Clouds consist of air that is a dispersion medium and the droplets of water act as a dispersed phase. They are aerosols.
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.
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.
Food Items: Day to day food items like soup, syrup, dairy products, etc.
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.
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.
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.
Delta formation consists of coagulation of the river particles with the help of the seawater electrolyte.
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.
1. What are colloidal solutions? Give some examples.
Colloidal solutions or colloidal suspensions are a mixture of substances that are suspended in a fluid. Although they can occur in all the three states of matter, be it a solid, a liquid, or a gas, colloidal solutions mostly refer to the liquid concoctions. In a true colloidal solution such as saltwater, the sodium chloride molecules get entirely mixed with water and this concoction can easily pass through the semipermeable membrane and not get divided.
On the other hand, the colloidal solutions have bigger molecules that do not liquify but are dispersed evenly throughout the solution. These molecules cannot pass through the semipermeable membranes as the true liquids do.
Given below are some examples of a colloidal solution.
Aerosols consist of the following:
They constitute of the following:
Emulsions are of the following types:
2. What is the difference between a colloid and a macromolecular solution?
The difference between a colloid and a macromolecular solution is as follows:
A colloid refers to a heterogeneous mixture of two or more different materials suspended in the same medium. They can usually be separated. Examples of colloids include fog, milk, and smoke.
Macromolecular solutions, on the other hand, are polymers that are dissolved in a solvent. An example of a macromolecular solution is starch which is dissolved in water. When you shine a light beam in any given colloidal suspension, you would notice that the light tends to get scattered along the path of the light beam. However, you would not see this phenomenon in the solutions.