What is a colloidal sol

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Systems are generally referred to as dispersions in which a finely divided phase (disperse phase, dispersed phase) is present in a surrounding phase (dispersant). The following table gives an overview of the possible dispersions:

Tab. 1
disperse phaseDispersantSurnameParticle sizesannotation
gaseousgaseousnot existent
liquidfoamapprox. 1 -1000
firmlysolid foamapprox. 1 -1000
liquidgaseousliquid aerosolapprox. 1 -1000
liquidemulsionapprox. 1 -1000
firmlysolid emulsionapprox. 1 -1000
firmlygaseoussolid aerosolapprox. 1 -1000
liquidSolSuspension: approx. 100-1000 Colloid: approx. 1 -100 sediments stable
firmlysolid solapprox. 1 -1000

The term colloid is used ambiguously:

  • The term colloid or colloidal solution describes a dispersion in which solid particles are dissolved in a liquid phase. It should be noted that these systems are not real solutions, but suspensions.
  • The term colloid is also used quite generally as a definition for the size of the structures of a system. Accordingly, all disperse systems whose particles or structures are in the size range from about 1 to 1000 are referred to as colloids.