Colloidal solutions have larger particles than those found in a real solution but smaller than those found in suspensions. The colloidal solution’s particles do not settle at the bottom when left undisturbed is another distinguishing trait that distinguishes it from suspension. 

A colloid is another name for a colloidal solution. It is a heterogeneous solution, yet it may appear to be a real solution due to the small particle size. The term ‘sol’ is used instead of ‘solution’ to distinguish a colloid from a simple solution, as in colloidal sol. Their particles are also referred to as colloidal particles. 

A colloid is a heterogeneous combination in which the particles are not as small as those in a solution but are so small that they cannot be seen with the human eye. Colloidal systems can exist in any three states of matter: gas, liquid, or solid. In contrast, a colloidal solution usually refers to a liquid mixture. A critical distinction between a real solution and a colloidal solution is the size of the constituent elements. 

Properties of Colloids

• Colour: The colloidal solution’s colour is determined by the wavelength of light scattered by the distributed particles. Depending on how the light is received by the observer, the colour of the colloidal solution changes. The finest gold sol is red, changing to purple, blue, and finally golden as the particle size rises. 
• Electrophoresis: When an electric current is passed through colloidal sols, they exhibit electrical features such as electrophoresis, in which colloidal particles tend to flow to oppositely charged electrodes. Electrophoresis tests confirm the presence of charge on colloidal particles. The movement of colloidal particles under an applied electric potential is known as electrophoresis. Positively charged particles are drawn to the cathode, whereas negatively charged particles are drawn to the anode. 
• Brownian movement: The colloidal particles in colloidal solutions appear to move in a continuous zig-zag pattern throughout the whole field of vision when examined through a strong ultramicroscope. The Brownian movement is the name given to this phenomenon. It is unaffected by the colloid’s nature, although it is affected by particle size and solution viscosity. 
• Colligative properties: The number of particles in a colloidal solution is smaller than the number of particles in a real solution because colloidal particles are bigger aggregates. As a result, the values of colligative properties are of low order when compared to absolute solution values at the same concentrations.
• Tyndall Effect: A homogeneous solution placed in darkness appears transparent when viewed in the direction of light; when viewed at right angles to the direction of the light beam, it appears perfectly dark. The bright cone of light is known as the Tyndall cone. Colloidal particles disperse light in all directions, which is why this happens.

Applications of Colloids

• Water contains several contaminants in the form of dispersed phase or colloidal particles. Alum is used to eliminate these contaminants.
• Because dirt and mud particles have an electric charge, they also act as colloidal particles in sewage disposal. Electrophoresis causes them to coagulate when they are passed across plates with the opposite charge.
• Before the smoke from the factories is released into the air, the hazardous particles in the smoke are eliminated. The smoke is transported through a chamber containing plates that have the opposite charge as the smoke particles. The charged plates attract the oppositely charged smoke particles, which lose their charge and drop to the bottom of the chamber in the form of a precipitate. 
• Colloids make up the majority of the medications we take. They are manufactured as colloids because this enhances their surface area and, as a result, their absorption by the body. 
• The colloidal characteristics of animal skin are due to positively charged particles.
• Latex, which comes from the rubber tree and is used to make rubber, is a colloid as well.
• Paints, cement, lubricants, synthetic polymers, and other industrial items are all made from colloids. They have the appropriate consistency and thickness due to their colloidal nature.

Types of Colloids

Conclusion

The mixture is called a colloidal solution or sol when the particles are even smaller (107 to 105cm, or 10 to 103 Ao). The size of the dispersed phase particles, rather than the number of molecules in each particle, is a distinguishing feature of these solutions. Many organic compounds with giant molecules (proteins, starch, gelatine, etc. ), silicic acids, aluminium hydroxide, and other substances can create sols. Because the dispersed phase has such a high degree of dispersion, the total surface area of its particles is enormous, and surface phenomena have a significant impact on the properties of colloidal solutions.