question_answer 19)

What are lyophilic and lyophobic sols? Give an example of each type. Why is hydrophobic sols easily coagulated?

Answer:

On the basis of the nature of interaction between the dispersed phase and dispersion medium, colloids are of two types: (i) Lyophilic sols. The colloidal system in which the particles of the dispersed phase have a strong affinity for the dispersion medium are called lyophilic sols. For example, gum, protein, starch. (ii) Lyophobic sols. The colloidal system in which the particles of the dispersed phase have no or very little interactions with the dispersion medium are called lyophobic sols. For example Fe(OH)3 and metal sulphides like As2S3. It requires a stabilising agent for preservation. Lyophobic sols are less stable since their stability is due to charge only. On the other hand, lyophilic sols are more stable since their stability is due to both charge as well as solvation of the particles. Thus, lyophobic sols are easily coagulated.