Question

Describe the important methods employed for the purification of a sol.

Answer 1

1. Dialysis: It involves removing dissolved impurities by placing the sol in a semipermeable membrane (like parchment) immersed in water. Impurities diffuse out, leaving the colloid behind.
2. Electrodialysis: An electric field is applied to speed up dialysis. Ions move towards electrodes, accelerating purification.
3. Ultrafiltration: Colloidal solutions are filtered through special ultrafilters that retain colloidal particles but allow impurities to pass.
4. Ultracentrifugation: The sol is spun at high speed to separate colloidal particles from impurities by settling them under centrifugal force.