Emulsion

Emulsion is a liquid containing in a suspension of microscopic droplets other, insoluble in them liquids. A typical example of a natural emulsion can serve as milk. Fats in the blood and lymph also are emulsified. Emulsification of fats in the intestine occurs with the participation of bile salts and is an essential stage of their absorption. Emulsion, as a rule, unstable - they are spontaneous droplets merge with each other (coalescence)that lead to delamination form the emulsion fluids. Technical emulsions are usually receive mechanical dispersion of one liquid in another excess in the presence of emulsifier - substances, preventing coalescence and, consequently, increasing the stability of the emulsion. Emulsifiers can be soap alkali and alkaline earth metals, fibers, rubber, etc. the Process of obtaining emulsion called emulsification, the destruction of emulsion - emulgirovanija.
Emulsions are of great importance in the preparation of many medicinal and cosmetic products, butter, cream, margarine, mayonnaise and other
Cm. also Dispersed systems.

Emulsii - the disperse systems consisting of two mutually insoluble liquids, one of which is distributed in the form of drops, sometimes visible only under a microscope. Both the liquid phase emulsions typically consist of molecules, sharply different in nature: if one fluid consists of polar molecules, then the other from a non-polar. Less polar phase in the emulsions used to be called "butter". A special position is occupied emulsion of mercury to which this classification is not applicable.
As a rule, emulsions get by dispersion of one liquid in another. Of the two pure liquids stable emulsions does not work as droplets merge (colesterol) and emulsion quickly stratified. The formation of stable emulsions is possible only in the presence of the so-called emulsifiers, which are adsorbed on the border of both liquids reliably, reduce surface tension. The presence of adsorption layers on the emulsion droplets often prevents them from merging. Sometimes to give E. sustainability, it is necessary to emulsifier created with mechanical strength protective membrane, preventing the merger drops. In some cases, such protective shells are formed by particles of powder, more often it is a film of polymers or polycolloid.
To obtain sustainable concentrated emulsion emulsifier should be entered in relatively large quantities, while for education diluted emulsions often enough only traces of surface-active substances.
Drops emulsions typically have the spherical form; in a very concentrated emulsions drops severely deformed. On structural-mechanical properties concentrated E. similar gels (see). Emulsions are usually unstable and decay in storage, mainly due to the coalescence of droplets, and the connection is very fine droplets into flakes [so-called occulation, or coagulation (see)], in which the individual droplets still exist.
To accelerate the destruction of the emulsions used a variety of techniques: centrifugation, the action of the electric field, adding electrolytes and non-electrolytes, etc. From non-electrolytes particularly strong destructive effect on emulsions stabilized gel films of proteins and polycolloid have some that have a high surface activity, but do not form a gel and a solid films on the surface. Sustainable E. form usually liquids with similar density.
Adding some substances emulsion type "oil in water" can turn into emulsii type water in oil" and Vice versa. This phenomenon has received the name "conversion phase emulsion". It can be called, for example, the introduction of emulsion emulsifier, stabilizing the opposite type emulsii. Emulsifiers different types simultaneous application of act antagonistically. Treatment phase with the introduction of emulsifier opposite type occurs gradually: first destroyed the original emulsion and there is an unstable system, which at the same time there are particles and original, and reverse E. along with complex formations, containing small drops of one phase included into bigger drops another (the so-called multiple E.), and only after vigorous mixing and the introduction of a sufficient quantity of emulsifier is full treatment phases.
Emulsions are of great practical value. Lipids are found in the blood of humans and animals in the form of finely dispersed emulsion (chylomicronemia E.), and the absorption and metabolism of fats is closely linked to their ability to formation of such emulsions. An example of a natural emulsion is milk. Derived from milk cream and butter and related artificially prepared systems (mayonnaise and margarine) also represent an emulsion. As emulsions are introduced into organism, many vitamins and medicinal substances. Concentrated emulsions are many ointment, medical candles and other pharmaceuticals. Cm. also Medicinal forms.