Types of Colloids





Different types of colloids are described below:

Reversible or Protective Colloids:

Certain substances such as gelatin, gum, starch etc. have a great affinity for the dispersion medium and easily pass into the colloidal solution. When they are coagulated, they can be easily brought back into colloidal state. Such types of the colloids are known as Reversible Colloids. Thus, “The substances which have great affinity for the dispersion medium and even after coagulation they can be directly converted into colloidal state, are known as reversible colloids.”

Reversible colloids are often uncharged particles, very stable and not easily coagulated by electrolytes. In fact, they are used to protect lyophobic sols e.g. addition of gelatin t6 Agl sol makes it more stable against electrolytes.

 

Lyophilic and Lyophobic Colloids:

Sols can also be classified on the basis of attraction or the affinity between the dispersed phase and the dispersion medium.

According to it, the solutions are divided into following two groups:

(i) Lyophilic colloids (Solvent loving): Substances which directly pass into colloidal solution when bought in contact with solvent are known as lyophilic colloids e.g. starch, gelatin, albumin are hydrophilic colloids (water loving colloids.)

(ii)  Lyophobic colloids (Solvent hating): Substances which do not directly pass into colloidal solution when brought in contact e.g. Metals, their sulphides and hydroxides are hydrophobic colloids (water hating colloids).



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