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Colloidal Dispersions

What is a Colloidal Dispersion?

Colloidal system or colloidal dispersion is a heterogeneous system which is made up of Dispersed phase and Dispersion medium. In colloidal dispersion one substance is dispersed as very fine particles in another substance called dispersion medium. In case of dust, solid particles are dispersed in air as dispersion medium.

Types of Colloidal Dispersions

Dispersed phase and dispersion medium can be solid, liquid or gas. Depending upon the state of dispersed phase and dispersion medium, eight different types of colloidal dispersions can exist.

Eight Different Types of Colloidal Dispersions are:

  1. Foam
  2. Solid foam
  3. Liquid Aerosol
  4. Emulsions
  5. Gels
  6. Solid Aerosol
  7. Sol (Colloidal suspension)
  8. Solid sol (Solid suspension)

Dispersed Phase Dispersion Medium Type of Colloidal Dispersions
Gas Liquid Foam
Gas Solid Solid foam
Gas Gas Does not exist
Liquid Gas Liquid Aerosol
Liquid Liquid Emulsions
Liquid Solid Gel
Solid Gas Solid Aerosol
Solid Liquid Sol or Colloidal Suspension
Solid Solid Solid sol(solid suspension)

It is important to note that when one gas is mixed with another gas, a homogeneous mixture is formed i.e. gases are completely miscible into each other. Colloidal dispersions are heterogeneous in nature and gas dispersed in another gaseous medium does not form colloidal system.

When the dispersion medium is gas, the solution is called Aerosol and when the dispersion medium is liquid, the colloidal dispersion is known as Sol. Sols can further be classified into different types depending upon the liquid used.

  • If the liquid used is water, the solution is Hydrosol or Aquasol.
  • If liquid used is Benzene, the solution is  Benzosol
  • If liquid used is Alcohol, the solution is Alcosol
  • If any organic compound is used, the solution is  Organosol

Example of Colloidal Dispersions

Different Types of Colloidal Dispersion and their examples are summarized in table below.

Type of Colloidal Dispersions Examples
Foam Soap, beer, lemonade
Solid foam Pumice stone
Does not exist
Liquid Aerosol Fog, dust
Emulsions Milk, rubber
Gel Butter, Cheese
Solid Aerosol Dust
Sol or Colloidal Suspension Paste, ink
Solid sol(solid suspension) Pearls, gem stones