Colloidal systems are formed by condensing a substance in a homogeneous medium (supersaturated solution, vapour, supercooled liquid), if the nucleation centres of a new dispersed phase, i.e. tiny droplets or crystals cannot grow to a size exceeding 10–5–10–4 cm. Condensation often accompanies chemical reactions that produce hardly soluble compounds. Another way of obtaining colloidal systems is spontaneous (in case of lyophilic systems) or forced (in case of lyophobic systems) dispersion. The existence of liquid aggregately stable lyophobic colloidal systems is always due to the presence in the dispersion medium of surface-active substances, i.e. stabilizers. These substances produce an adsorption-solvate protective layer on the particle surfaces and prevent the close approach and coagulation of particles under the action of short-range forces of molecular attraction. The close approach of particles may be impeded by the disjoining pressure of the liquid dispersion medium, which is solvated by molecules or ions of the stabilizer in the adsorption layer; by electrostatic repulsion of like-charged ions adsorbed on the particle surfaces; or by enhanced structural viscosity of the surface protective layer, the so-called structural-mechanical barrier. Various types of colloidal systems are presented in the Table.
Type of colloidal system
Aerosol of liquid particles
Fog, haze Solid
Aerosol of solid particles
Ruby glass, pearl
- Goldt Ilya V.
- Shlyakhtin Oleg A.
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