External colloid refers to a type of colloidal system in which the dispersed phase is present outside a continuous medium or phase. Colloids are heterogeneous mixtures consisting of small particles dispersed throughout a medium, where the particles are typically between 1 and 1000 nanometers in size. These particles can be solid, liquid, or gas, and the medium can also be solid, liquid, or gas.
In the case of an external colloid, the dispersed phase particles are located externally or outside the continuous medium. This means that the particles are not dissolved within the medium or evenly distributed throughout it, but rather exist as separate entities on the outside.
External colloids can be observed in various natural and synthetic systems. For instance, oil droplets in water can form an external colloid, where the oil droplets remain separate from the water in which they are dispersed. Similarly, cream is an example of an external colloid, where tiny globules of fat are dispersed in a liquid medium (milk).
External colloids have unique properties and behavior compared to their counterpart, internal colloids, where the dispersed phase is located internally or within the continuous medium. Understanding external colloids is crucial in various fields, including chemistry, materials science, and pharmacology, as they play a significant role in the behavior and properties of colloidal systems.
