Question

Peptisation is a process in which:
A. precipitation becomes the true solution.
B. true solution becomes a suspension.
C. A colloid gets coagulated.
D. A suspension gets converted into a colloid.

Answer 1

In dispersion methods, large particles are broken down in the presence of dispersion medium. The products formed are stabilized by adding mechanical energy input. Peptisation is a type of dispersion method. The cause of peptisation is the adsorption of ions of electrolyte by the particles of precipitate.

Complete step by step answer:
A colloid is a substance microscopically dispersed throughout another substance. They can be made to settle by the process of centrifugation. Colloidal mixture has particles that are not as small as solution and not as large as a suspension. The particles in a suspension can be distributed throughout the suspension evenly by shaking the mixture.
Separation of colloids can be done by four methods-mechanical dispersion, electrical dispersion, peptisation and condensation method. Peptisation is a method of converting a freshly prepared precipitate into colloidal form by adding suitable electrolyte called peptizing agent or stabilizing agent. Major peptizing agents are sugar, gum, gelatin and electrolytes.
Hence peptisation is a process in which a suspension is converted into a colloid.
Thus, the correct option is D.

Additional information:
Peptization can be minimized by washing a precipitate with a solution of an electrolyte that is volatilized during an ensuing drying step. This is the reverse of coagulation. Coagulation is the process of converting colloidal suspension to a filterable solid by heating, stirring and adding of an electrolyte.

Note:
Colloidal particles cannot be washed with pure water because peptization occurs. The second electric layer is removed but the first layer remains on all particles with an electric charge of the same sign. The result is that there is a return to the repulsive state and begin once again to separate as colloidal particles.