Peptization is an important concept in colloid chemistry. Here’s a clear explanation:
Peptization
- Definition: Peptization is the process of converting a freshly precipitated substance into a colloidal solution by adding a small amount of an appropriate electrolyte (called a peptizing agent).
- How it works:
- The electrolyte ions adsorb on the surface of the precipitate particles.
- This prevents the particles from aggregating again and imparts them an electrical charge.
- As a result, the particles disperse uniformly throughout the medium, forming a stable colloidal sol.
- Example:
- Freshly prepared ferric hydroxide precipitate + a little FeCl₃ solution → Fe(OH)₃ colloidal sol.
- Silver chloride precipitate + a little AgNO₃ → AgCl sol.
- Importance:
- Used in the preparation of many lyophobic colloids (like sols of metals and their oxides).
- Explains why washing precipitates repeatedly with water can sometimes cause loss of the substance (as it turns into a colloidal sol).
In short: Peptization is the conversion of a precipitate into a colloidal sol by adding a peptizing agent (electrolyte), which stabilizes the particles by giving them charge.