Colloidal Dispersions

What Is A Colloid?
The definition of a colloid is anything that can be broken down into the smallest possible part while still retaining the same characteristics of its whole.
For example: Fog is a colloid of rain or water. Flour is a colloid of wheat.

Colloidal Solution
A special type of liquid mixture of suspension in which the particles of suspended liquid or solids are present in very finely divided form (i.e., particle size from about 1-500 millimicrons in diameter). The colloidal suspension of liquids in liquids is an emulsion.

Unlike ordinary suspensions, colloids do not exhibit the phenomenon of settling to a noticeable degree. Because of their exceedingly high ratio of surface area to volume, the rate of sedimentation is very slow, so that the slightest convection currents (as from small temperature differences) are sufficient to keep the particles in uniform distribution.

The suspended particles may contain a few molecules to hundreds of molecules of small or average size. Such particles are actually too small to be seen by the ultra microscope, but can be studied by means of reflected light, and can be resolved by the electron microscope. Suspensions in which the particles are very large molecules (proteins, polymers, etc.) may behave like colloids even though the particles are single molecules as large as half a micron in diameter. The realm of colloids also includes suspensions of finely divided liquids or solids in gases (fogs and smokes) and systems of thin films, bubbles or filaments whose thickness is of the above dimensions.

Colloidal Dispersions in General and the Difference Between Metallic and Plant Derived Colloidal Minerals. Chemical species present in water may be considered to physically occur in a variety of modes. These modes define an essentially continuous series which can be referred to as the solute/colloid/suspended particle continuum. While the pure end member modes are easily conceptualized as: a) dissolved ions or molecules; and b) macroscopic particles, the intermediate modes require further explanation. The word 'colloid' as used here collectively identifies the intermediate continuum of modes. Chemical species which may be referred to as 'colloidal' include: a) discreet chemical species with sufficient size or mass to behave as colloids (large macromolecules); b) amorphous or crystalline chemical compounds which exist in the solid phase as colloids; c) collections of a few to hundreds of smaller molecules which form species of colloidal dimension (aggregates); and d) chemical species who are associated with colloids (usually by adsorption) and whose behavior is controlled by the colloids.

A colloidal system is more easily described than a colloid itself, and is described as a two-phase system in which one phase is uniformly and permanently distributed or dispersed in the second phase. This is in contrast with both a true solute/solvent system, which comprises a single phase, and a suspended-particle/solvent system which is a two phase system but is typically not uniform and never permanent. Although natural colloidal systems exist for every binary combination (except gas-in-gas) of solid, liquid and gas phases (e.g., fog is a liquid-in-gas colloidal system, emulsions are liquid-liquid systems), the most geochemically relevant systems are those with an aqueous dispersing media and dispersed solid particles, known as sols. Chemically, colloids behave like solids requiring consideration of surface area and charge and other aspects of heterogeneous reaction theory. Physically or hydro dynamically however, colloids behave somewhat like solutes principally because of their small size.