Question

why peptising agent is add to convert ppt onto colloidal solution

Answer 1

For example,when we add a small volume of very dilute hydrochloric acid solution( peptizing agent) to a fresh precipitate of aluminum hydroxide,it leads to formation of an aluminum hydroxide

Answer 2

The process of peptization involves the conversion of a precipitate into colloidal sol by shaking it with dispersion medium in the presence of small amount of electrolyte.The electrolyte used for this purpose is called the peptizing agent