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Colloids are one of the three primary mixtures. Its particles that range between 1 and 1,000 nanometers is perfectly dispersed in a mixture and do not settle at the bottom of the container; hence they are called colloidal dispersion.

The substance in a colloid during the dispersed phase must be larger than a molecule but smaller than the particles that can be seen by the naked eye. If the dimensions are smaller, it will be considered a solution and not a colloid; if it is larger, it becomes a suspension.

Colloids Classification

According to Libretexts, there are four classifications of colloids: sol, emulsion, foam, and aerosol.

Sol colloids are a colloidal suspension are made of very small solid particles in a liquid medium. In contrast, an emulsion is a mixture of two liquids that are usually immiscible, like oil and water.

Foam is another type of colloid formed when gas particles are trapped inside a liquid or solid. Lastly, aerosol contains liquid droplets or solid particles in a gas.

Applications of Colloids

The Fact Factor has categorized colloids applications that are usually seen in nature, agriculture, food, industry, and medicine. Here are some of them:

Nature

Even in nature, colloids are everywhere. One example of that is the blue sky, wherein the light scatters when the particle is smaller than the wavelength of the light. The sky turns blue due to the scattering of light on the small particles.

Another example of colloids in nature is the sky's red-orange color during sunrise and sunset, the blue color of the sea, fog mist, and rain. The Tyndall effect is responsible for the blue color of the sea.

Industrial Application

Colloids are also popular in the industry as they can be applied in thickening agents, paints, ink, rubber, leather tanning industry, the cleansing action of soaps, disinfectant, metallurgy, asphalt emulsion for roads, rubber, cement, graphite, lubricants, and many more.

Furthermore, colloids are also observed in the making of photographic plates, sewage precipitation, and smoke precipitation.

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Colloids in Food

Most of the foods today are colloidal. Colloids in food help it give the "mouthfeel" texture, which allows it to melt as it touches the warmth of the mouth.

Some examples of food that are colloids are dairy products like milk and butter, fruit juices, and eggs. The raw egg is a type of sol colloid of a long chain of proteins that are all curled up due to the hydrogen molecule bonding between different parts of the molecule.

Agriculture

Colloids are also in the field of agriculture, starting with the most basic: the soil. Fertile soil is a colloid in which the humus acts as a protective colloid.

Another example is the formation of a delta, which happens when the river water, a colloidal solution of clay with a negative charge, and the seawater have a positive charge meet. It forms coagulation that makes clay particles aggregate and settles down in the water.

Medicine

Colloidal medicines are more effective as they can act on a larger area of the body. There are many applications of colloids in medicine, but the most basic form of colloids in this field is the blood, which is a colloidal solution of albuminoid substances.

For example, clotting. When the flesh is cut, and blood comes out, a solution of concentrated ferric chloride is applied to clean it. Coagulation of the blood then takes place, and a clot is formed to prevent further bleeding.

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