PHYSICAL CHEMISTRY IN BRIEF

CHAP. 14: DISPERSION SYSTEMS [CONTENTS] 457

Dispersion environment Dispersion phase Term used for the system

Gas Liquid Mist

Gas Solid Smoke (Dust)

Liquid Gas Foam

Liquid Liquid Emulsion

Liquid Solid Colloid solution, suspension

Solid Solid Solid foam, porous substance

Solid Liquid Solid emulsion

Solid Solid Solid sol, eutectic alloy

Based on the particle size, dispersion systems are classified as

• Analytical dispersions with the particle size less than 5 nm,


• Colloid dispersions with the particle size ranging from 5 to 100 nm.


• Microdisperions with the particle size ranging from 100 nm to 10μm,


• Coarse dispersions with the particle size over 10μm.

Note:Analytical dispersion systems rank rather among homogeneous systems. Microdis-

persions and coarse dispersions are usually ranked among suspensions.

The above list was only a simplified classification of dispersion systems. Only very rarely do
these systems contain only one single size of particles. Such systems are classified asmonodis-
persions. In most systems, the dispersion ratio exists simultaneously in a continuous distri-
bution of different particle sizes, and the system is termedpolydispersion.
Based on thedispersed ratio structure, dispersion systems may be classified as:

• systems with isolated (often roughly spherical) particles calledsols,


• systems with an interlinked structure of the dispersion phase forming a net structure in
  the dispersion environment, which are calledgels.
  The names given to individual dispersion systems often combine the particle shape and the
  phase of the dispersion environment. Sols with air as the dispersion environment are referred
  to as aerosols while those with liquid as the dispersion environment are called lyosols (lyos =
  liquid).