Colloidal State Topics  

   
______________________________________________________________

Classification of colloids based on Physical state



Colloidal systems (colloidal solutions) are heterogeneous in nature and consist of following two phases: 

(i) Dispersed phase: The substance present in the form of colloidal particles in a colloidal system constitutes the dispersed phase. Thus, the dispersed phase may be defined as the phase constituting the colloidal particles. For example, in a colloidal solution of ferric hydroxide in water, the ferric hydroxide particles are of colloidal size and constitute the dispersed phase. 

(ii) Dispersion medium: The medium in which the colloidal particles are dispersed is called dispersion medium. For example, in the colloidal solution of ferric hydroxide in water, water is the dispersion medium. 

Classification Based on Physical State of Dispersed Phase and Dispersion Medium. 
Depending upon the physical state of the dispersed phase and dispersion medium, eight types of colloidal systems are possible. These are described in the table given below: 

 

S.No.

Dispersed phase

Dispersion medium

Common name of the system

Examples

1.

Solid

Solid

Solid sol

Gems, ruby glass, coloured glasses, pigmented plastics etc.

2.

Solid

Liquid

Sol

Gold sol, sulphur sol, ferric hydroxide sol, As2S3 sol, ink, most of the paints, starch dispersed in water, muddy water etc.

3.

Solid

Gas

Aerosol of solids

Smoke, dust etc.

4.

Liquid

Solid

Gel

Cheese, butter, boot polish, jellies etc.

5.

Liquid

Liquid

Emulsion

Milk, emulsified oils, medicines etc.

6.

Liquid

Gas

Aerosol of liquids

Fog, mist, clouds, Liquid sprays etc.

7.

Gas

Solid

Solid foam

Pumice stone, styrene foam, foam rubber etc.

8.

Gas

Liquid

Foam or Froth

Lemonade froth, soap lather, shaving cream foam etc.

 


                                  Table: Types of Colloidal Systems 


   
____________________________________________________________

Classification of colloids based on Physical State



It is to be noted that the colloidal system of a gas into some other gas is not possible because a gas mixed with some other gas always forms a homogeneous gaseous solution. Since colloidal systems are heterogeneous, they cannot be obtained by dispersing a gas into some other gas. 

Among the various types of colloidal systems listed above, the more common and more important ones are sols (solids dispersed in liquid), gels (liquids dispersed in solids) and emulsions (liquids dispersed in liquids). 

Sol is a general term and refers to a colloidal system obtained by dispersing a solid into a liquid. Depending upon the nature of dispersion media, sols are usually given different names. For example, sols consisting of water as dispersion medium are usually called hydrosols. Those consisting of alcohol as dispersion medium are termed as alcosols, while those having benzene as the dispersion medium are referred to as benzosols. Similarly, aerosols are the colloidal system having air as the dispersion medium. 
Related Resources
Applications of Colloids

Applications of Colloids Colloids play a very...

Colligative Properties of Colloidal Solutions

Colloidal State Topics Introduction to Colloidal...

Preparation of Colloidal Solutions

Colloidal State Topics Introduction to Colloidal...

Electrical Properties of Colloidal Solutions

Electrical Properties of Colloidal Solutions Some...

Summary of Surface Chemistry

Colloidal State Topics Introduction to Colloidal...

General Physical Properties of Colloidal Solutions

General Physical Properties of Colloidal Solutions...

Mechanical Properties of Colloidal Solutions

Colloidal State Topics Introduction to Colloidal...

Classification of Colloids based on Nature of Interaction

Classification of Colloids based on Nature of...

Keywords of Surface Chemistry

Keywords of Surface Chemistry 1. Adsorption 2....

Protective Colloids and Gold Number

Protective Colloids and Gold Number Lyophobic sols...

Emulsions

Colloidal State Topics Introduction to Colloidal...

Optical Properties of Colloidal Solutions

Optical Properties of Colloidal Solutions Optical...

Purification of Colloidal Solutions-Part1

Purification of Colloidal Solutions (Sols)...