Everyday Uses and Protective Actions of Colloids Explained
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.
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.
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.
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.
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.
FAQs on Real-World Applications of Colloids in Chemistry
1. What is a colloid, and what are some common examples we see in daily life?
A colloid is a mixture in which one substance of microscopically dispersed insoluble particles is suspended throughout another substance. The size of the dispersed particles ranges from 1 to 1000 nanometres. Unlike a true solution, the particles do not dissolve, and unlike a suspension, they do not settle out. Common examples from daily life include:
Milk: An emulsion of liquid fat globules in water.
Fog/Mist: An aerosol of water droplets in the air.
Jelly: A gel, which is a liquid dispersed in a solid medium.
Paint: A sol, with solid pigment particles dispersed in a liquid.
2. What are the most important real-world applications of colloids in industry and daily life?
Colloids have numerous significant applications across various fields. Some of the most important include:
Food Industry: Products like ice cream, cheese, butter, and fruit jellies are all colloidal in nature, relying on colloidal properties for their texture and stability.
Medicines: Many pharmaceuticals are emulsions or sols. Colloidal gold and silver have antiseptic properties, and medicines are often prepared in colloidal form for easier absorption by the body.
Water Purification: Alum is used to coagulate and settle suspended impurities, which are colloidal, making water fit for drinking.
Pollution Control: The Cottrell smoke precipitator uses the principle of coagulation to remove colloidal smoke and dust particles from industrial emissions.
Rubber and Paint Industries: Rubber is obtained by the coagulation of latex (a colloid), and paints are colloidal solutions of pigments.
3. How is a colloid different from a true solution and a suspension?
The primary differences lie in particle size, stability, and interaction with light. A true solution has particles smaller than 1 nm, is transparent, and does not scatter light. A suspension has particles larger than 1000 nm, is unstable (particles settle over time), and is often opaque. A colloid falls in between, with particle sizes of 1-1000 nm. It appears translucent or cloudy, remains stable, and exhibits the Tyndall effect (scattering of light), which is a key distinguishing feature.
4. How do colloids play a role in the purification of drinking water?
Natural water often contains suspended impurities like clay and mud, which are negatively charged colloidal particles. These particles are too small to be filtered out easily. To purify the water, a coagulant like alum is added. The alum provides highly positive ions (Al³⁺), which neutralize the charge on the colloidal impurities. This process, called coagulation, causes the particles to clump together, become heavy, and settle down, allowing for their easy removal by decantation or filtration.
5. Why are colloids, specifically emulsions and sols, so important in the pharmaceutical and food industries?
Colloids are crucial in these industries for creating stable and effective products. In pharmaceuticals, many drugs are poorly soluble in water. Formulating them as a colloid (emulsion or sol) improves their stability, bioavailability, and allows for controlled delivery, as seen in creams and lotions. In the food industry, colloids are fundamental to the texture and shelf-life of many products. For example, milk is an emulsion, and mayonnaise is stabilised by an emulsifying agent. Colloids provide the desired consistency and prevent ingredients from separating.
6. What is the Tyndall effect, and how does it demonstrate the presence of a colloid?
The Tyndall effect is the scattering of a beam of light by colloidal particles, which makes the path of the light visible. This phenomenon occurs because the particles in a colloid are large enough to interfere with and scatter the light waves. True solutions do not show this effect because their constituent particles (ions or small molecules) are too small to scatter light. Therefore, shining a laser pointer through a liquid is a simple and effective test: if the beam's path is visible, the liquid is a colloid.
7. How is the formation of a river delta an example of a natural colloidal application?
River water contains colloidal particles of clay and sand, which carry a negative charge. Seawater is rich in electrolytes, containing positive ions like Na⁺ and Mg²⁺. When river water flows into the sea, the electrolytes from the seawater neutralize the charge on the suspended clay particles. This causes the colloidal particles to coagulate and precipitate. Over many years, this continuous deposition of coagulated material at the river mouth builds up to form a delta.
8. In what way does the charge on colloidal particles contribute to the function of a Cottrell smoke precipitator?
A Cottrell precipitator is an air pollution control device that relies on the electrical properties of colloids. Smoke is an aerosol containing charged colloidal particles of carbon and dust. The precipitator consists of plates carrying a charge opposite to that of the smoke particles. When smoke is passed through it, the charged colloidal particles are attracted to the oppositely charged plates. They lose their charge, get precipitated, and are collected, allowing clean air to escape from the chimney. This entire process is an application of electrophoresis.
9. Why is milk considered a complex colloid, and what makes it stable?
Milk is considered a complex colloid because it is not just one type. It is primarily an emulsion of liquid fat globules dispersed in water. Additionally, it contains proteins like casein, which exist as a colloidal sol. The stability of milk is largely due to the casein protein, which acts as a natural emulsifying agent. Casein forms a protective layer around the fat globules, preventing them from clumping together and separating out, thus keeping the emulsion stable.
10. How are colloids used in the tanning of animal hides to produce leather?
The process of tanning leather is a direct application of colloid chemistry. Animal hides are composed of protein, which forms a positively charged colloidal solution. Tanning solution, typically derived from tannin (from bark), contains negatively charged colloidal particles. When the hide is soaked in the tanning solution, mutual coagulation occurs. The oppositely charged particles neutralize each other, causing the protein to harden. This process makes the leather tough, water-resistant, and prevents it from rotting.
