The suspended particles that do not settle in a solution are called colloids. The Tyndall Effect is a phenomenon in which light beams incident on colloids are dispersed, resulting from light and colloidal matter interactions. Colloids are made up of chemicals that are uniformly distributed in one another. The dispersed phase is the substance distributed in these combinations, while the continuous phase is the substance through which it is disseminated.

Define Colloidal Solutions?

A colloidal solution is a combination of particles of different substances. These soluble/insoluble particles are microscopically disseminated and suspended in a fluid regularly. They usually depict a solution system whose particles have a particle size somewhere between a genuine solution and a coarse dispersion, approximately ranging from 1 nm to 500 nm. In some instances, a colloidal solution can be a two-phase system, whereas, in others, it can be a one-phase (homogeneous) system.

Classification of Colloids

The colloids are classified into three types –

• Based on physical state: aerosols, gels and emulsions of various kinds
• Based on dispersion medium: hydrosols, alcohols and aerosols are some examples of the colloids based on dispersion medium.
• Based on interaction medium: The interactions between the tensions of a dispersion medium and the dispersed phase determine the varieties of colloidal solutions. They are further subdivided into lipophilic, lyophobic and association colloids.

Preparation of Colloidal Solution

Colloidal solution is prepared in two ways:

• Condensation method: The condensation method requires oxidation, hydrolysis and excessive cooling for the preparation of Colloidal solution. 
• Dispersion method: The dispersion method utilises mechanical dispersion, electrical dispersion and peptisation for preparing colloidal solution.

Properties of Colloidal Solution

Optical Properties

The Faraday-Tyndall effect – When a powerful beam of light is sent across the colloidal sol, the light scattering by the particles produces a visible cone. The Faraday–Tyndall effect is what causes this.

Scattering of Light – The Faraday-Tyndall Effect is responsible for the light scattering properties of colloidal solution particles. The blue colour of the sky, which is visible to human eyes due to the scattering of blue wavelength light by colloidal particles in the atmosphere, is a beautiful illustration. This feature determines the molecular weight of colloidal particles.

Electrical Properties 

Donnan Membrane Equilibrium – When sodium chloride is added to a solution on the first half of a semipermeable membrane and a negative charges colliding with its counter ions R-Na+ is placed on the other, the sodium and chloride ions can freely travel over the barrier, but the colloidal anionic particles cannot.

Kinetic Properties

Brownian Motion –The random dispersion of colloidal particles is described by Brownian motion. The irregular motion, which can be seen with particles as large as 5 m, was attributed to the particles being bombarded by the molecule of the dispersion medium. Because the molecules are too small to perceive, their motion cannot be monitored. The speed of the molecules increases as the particle size decreases. Osmotic pressure is described by the Van’t Hoff Equation. 

Viscosity – Viscosity is a measure of a system’s resistance to flow when it is subjected to a force. When a liquid is denser, it takes more force to move and keep it moving at a consistent rate.

Sedimentation – Because the colloidal particles are always in Brownian motion, they have little tendency to silt. The colloidal particles’ Brownian motion is sufficient to counteract the gravitational force acting on them. As a result, a larger force is required to achieve quantitative and detectable sedimentation of colloidal particles.

Application of Colloids

Colloids are widely used in medical, food and other industries. Some of the popular uses of colloids are as follows: 

• Colloids are widely used in the food industries.
• Leather industry also depends heavily on colloidal solutions for cleaning and utilising leather and producing different handicrafts. 
• There are several medicines available today, which are colloidal and are used to treat many diseases or infections.

Conclusion

Colloidal solution is useful in various ways in chemistry. Different electrical, physical and other properties are used in various industries for other products. Composition, packing arrangement, particle size and degree of regularity all influence the bulk properties of a colloidal crystal.