Dispersion (chemistry)

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

Overview

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 ...)
Dispersion medium	liquid	emulsion	foam	suspension
	gaseous	Aerosol , liquid (mist)	Gas mixture, no dispersion!	Aerosol, solid ( smoke )
	firmly	porous solid (solid foam), soaked through	porous solid (solid foam), dry	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).

Examples

designation	disperse phase	Dispersion medium	Examples
Dispersion	Solid and liquid	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

literature

• AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 .
• G. Lagaly, O. Schulz, R. Zimehl: Dispersionen und Emulsionen , Steinkopff, Darmstadt 1997. ISBN 3-7985-1087-3 .

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.