Dispersion (chemistry)

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In colloid chemistry and process engineering, a dispersion is a heterogeneous mixture of at least two substances that do not or hardly dissolve in one another or chemically combine with one another. One or more substances (disperse phase ) are finely distributed in another continuous substance (dispersion medium).

  • Synonyms for disperse phase: dispersed phase, internal phase, secondary phase
  • Synonyms for dispersion medium: dispersant, dispersant, continuous phase, outer phase, main phase

The individual phases can be clearly delimited from one another and, as a rule, separated from one another again by physical methods (e.g. filtering , centrifuging ), or they separate themselves ( sedimentation ).

Classification according to particle size

According to their particle size, disperse phases can be classified as follows:

designation Particle size example
dissolved in a molecularly disperse manner <1 nm real solution / fluid phases
dissolved in a colloidal disperse 1 nm to 1 µm Protein solutions
roughly dispersed > 1 µm Milk fat globules

If all the particles in a dispersion are approximately the same size, one speaks of a monodisperse, homodisperse or isodisperse system; if the particle sizes are different, it is called heterodisperse or polydisperse systems.

Classification according to physical states


With two-phase dispersions, there are a total of eight types of dispersion, depending on the aggregate states :

  disperse phase
liquid (in ...) gaseous (in ...) fixed (in ...)
liquid emulsion foam suspension
gaseous Aerosol , liquid
Gas mixture,
no dispersion!
Aerosol, solid
( smoke )
firmly porous solid
(solid foam),
soaked through
porous solid
(solid foam),
solid mixture,
dense structure

Viewed microscopically, a gas mixture is always homogeneous and therefore not a dispersion (this also applies if there are concentration gradients viewed macroscopically).


designation disperse phase Dispersion medium Examples
Dispersion Solid and
liquid Polymer dispersion , milk ( milk fat is emulsified, casein is suspended), cocoa (drink)
Solid mixture
solid mixture
Solid Solid Granite , conglomerate (rock) , gravel in concrete ,
pigments in hardened paints
suspension Solid liquid Lime milk , scouring milk , naturally cloudy apple juice ,
jam , glacier milk
Aerosol Solid gas Smoke , fine dust in the air, sandblasting , sandstorm ,
pyroclastic flow , snowfall
inclusion liquid Solid wet bath sponge , cloudiness in amber ,
damp porous brick
emulsion liquid liquid Milk , butter
skin cream , suntan lotion
Aerosol liquid gas Fog , rain clouds
porous body,
solid foam
gas Solid Foam , aerated concrete , metal foam
Air bubbles in ice
foam gas liquid Soap foam, sparkling wine , cola foam,
fire extinguishing foam
designation disperse phase Dispersion medium Examples
Biofluid Erythrocytes liquid blood
Biocolloid Apatite Collagen bone
gel Macromolecules solvent Glues , gels
Micelles Aggregates liquid Soap , dyes


Individual evidence

  1. Wilfried J. Bartz: Expert Practice Lexicon Tribology Plus: 2010 Terms for studies and work . expert verlag, 2000, ISBN 3-8169-0691-5 , p. 36 ( limited preview in Google Book search).
  2. a b c Müfit Bahadir, Harun Parlar, Michael Spiteller: Springer Umweltlexikon . Springer, 2000, ISBN 3-642-56998-6 , pp. 328 ( limited preview in Google Book search).
  3. See Gerhard Lagaly , Oliver Schulz, Ralf Zimehl: Dispersionen und Emulsionen . An introduction to the colloidics of finely divided substances including clay minerals . Steinkopff, Darmstadt 1997, ISBN 3-7985-1087-3 , p. 3.