The colloids are Homogeneous mixturesAs with solutions, but in this case on a microscopic scale, particles of one or more substances are distinguished, the dispersed or discontinuous phase, which are dispersed in another substance called the dispersing or continuous phase.
The word colloid was introduced by Scottish chemist Thomas Graham in 1861 and is derived from the Greek root kolas (κoλλα), which means “that adheres"Or"unctuous”, This is related to property of this type of substances not to pass through the usual filters.
In the colloids, the particles in the dispersed phase are large enough to scatter light (an optical effect known as the Tyndall effect), but not so small as to precipitate and separate. The presence of this optical effect makes it possible to distinguish a colloid from a solution or solution. Colloid particles have a diameter between 1 nanometer and a micrometer; that of solutions are smaller than 1 nanometer.The aggregates that make up the colloids are called micelles.
The physical state of the colloid is defined by the physical state of the dispersing phase, which can be liquid, solid or gaseous; the dispersed phase can also correspond to one of these three types, although in gaseous colloids this is always a liquid or a solid.
Colloidal substances are important in the formulation of numerous industrial materials of common and massive use, such as paints, plastics, insecticides for agriculture, inks, cements, soaps, lubricants, detergents, adhesives and various food products. The colloids contained in the soil contribute to its retention of water and nutrients.
In medicine, colloids or plasma expanders are administered to expand the intravascular volume for longer periods of time than is achieved through the use of crystalloids.
Colloids can be hydrophilic or hydrophobic. Surfactants such as soaps (salts of long chain fatty acids) or the detergents they form association colloids, allowing the stabilization of hydrophobic colloids.
When a clear distinction can be made between the dispersed phase and the dispersing medium, it is called a simple colloid. There are other more complex colloids, such as reticular colloidal systems, in which both phases are formed by interlocking networks (composite glasses and many gels and creams are of this type), and the so-called multiple colloids, in which the dispersing medium coexists with two or more dispersed phases, which are finely divided. Twenty examples of colloids are given below:
- Milk cream
- Milk
- Latex paints
- Foam
- Jelly
- Fog
- Smoke
- Montmorillonite and other silicate clays
- Organic material
- Bovine cartilage
- Albumin derivatives
- Plasma
- Dextrans
- Hydroethyl starches
- Woven bone
- Smog
- Detergents
- Silica gel
- Titanium oxide
- Ruby
