1. There are no strict boundaries on the size of colloidal particles, but they tend to vary between 10-9 m to 10-6 m in size.

2. Figure 17.22: The Tyndall effect
Source: Stock Boston

4. Figure 17.23: Representation of two colloidal particles

6. Type of Colloids Dispersing medium Dispersed phase Name Solid
Solid sol
Liquid
Gel
Gas
Solid foam
Sol
Emulsion
Foam
Solid aerosol
Aerosol

7. Aerosols:
Man-made: Aerosol sprays, insecticide spray, smog. Natural: Fog, clouds.
Solid aerosol:
Natural: Smoke, dust.
Foam:
Man-made: Shaving lather, whipped cream.
Emulsions:
Man-made: Mayonnaise, cosmetic lotion, lubricants. Natural: Milk.
Sols:
Man-made: Paint, ink, detergents, rubber (a latex - also occur naturally).
Solid foams:
Man-made: Marshmallow, styrofoam, insulation, cushioning.
Gels:
Man-made: Butter, jelly.
Solid sols:
Man-made: Certain alloys. Natural: Pearl, opal.
Biological macromolecules and cells may be considered to be biocolloids and many foods are also colloidal in nature. Colloids are also an important feature of the natural environment.

8. Colloids in Paint and Food

9. Cottrel precipitator installed in a smokestack.

10. Magnetic liquid seal

12. Surfactant

13. cmc = critical micelle concentration

15. Vesicles in Cell