Colloid:

Particles so fine that they do not settle if they do not undergo a previous coagulation. Its size ranges between 10 and 1000 angstroms. It has a negative net charge, and obstructs membranes. These can be bacteria, silica and clay.


Finely divided solids that do not settle but can be removed by coagulation, biochemical action, or membrane filtration; they constitute an intermediate point between a true solution and a suspension.


Dispersions of finely divided particles of one material (dispersed phase) in another, called dispersion medium.

In general, colloidal particles have a size that varies between 10 and 10,000 amstrongs.


They are distinguished from common molecules by their inability to diffuse through the membranes that allow molecules and ions to pass freely.


Dispersion of a finely divided solid (the dispersed phase) in a liquid (the dispersing medium), which is generally negatively charged.


Both the suspended or dispersed phase and the suspension medium can be solid, liquid or gaseous, although the dispersion of one gas in another is not known as colloidal dispersion.


An emulsion is a colloidal dispersion of liquid particles in another liquid; mayonnaise, for example, is a suspension of tiny globules of oil in water.


A "sun" is a colloidal suspension of solid particles in a liquid; The paints, for example, are a suspension of tiny solid pigment particles in an oily liquid.


A gel is a sun in which the suspended particles are loose, arranged in a dispersed, but defined three-dimensionally, giving some rigidity and elasticity to the mixture, as in gelatin.


The particles of a real colloidal dispersion are so small that the incessant shock with the molecules of the medium is sufficient to keep the particles in suspension; The random movement of particles under the influence of this molecular bombardment is called Brownian motion.


However, if the force of gravity increases markedly by a high-speed centrifuge, the suspension may break and the particles may precipitate.


In soil physics, discrete mineral particles less than 2 um in diameter. Material of very small size, in the range of 10-5 to 10-7 in diameter.