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Explain about coagulation of lyophilic sols and protection of colloids. |
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Answer» Solution :Coagulation of lyophilic sols : There are two factors which are responsible for the stability of lyophilic sols. These factors are the charge and solvation of the colloidal particles. When these two factors are removed a lyophilic sol can be coagulated. This is done (i) by adding an electrolyte and (ii) by adding a suitable solvent. When solvents such as alcohol and acetone are added to hydrophilic sols the dehydration of DISPERSED phase occurs. Under this condition a small quantity of electrolyte can bring about coagulation. Protection of colloids : Lyophilic sols are more stable than lyophobic sols. This is due to the FACT that lyophilic colloids are extensively solvated, i.e., colloidal particles are covered by a sheath of the liquid in which they are dispersed. Lyophilic colloids have a unique property of protecting lyophobic colloids. When a lyophilic sol is added to the lyophobic sol, the lyophilic particles form a LAYER around lyophobic particles and THUS protect the latter from electrolytes. Lyophilic colloids USED for this purpose are called protective colloids. |
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