Question

What is the hardy Schulze rule?

Answer 1

Hardy Schulze rule

• “The greater the valency of the flocculating ion added, the greater its power to cause precipitation. This is known as the Hardy-Schulze rule.”
• For the coagulation of negative sol, the positive charge on ions must be high.
• The flocculating power for the coagulation of a negative sol is in the following order:

${\mathrm{Al}}^{3+}>{\mathrm{Ba}}^{2+}>{\mathrm{Na}}^{+}$

• The charge on $\text{Al}$ is higher as compared to $\text{Ba}$, and $\text{Na}$. So, the flocculating power for the coagulation of a negative sol is higher for ${\mathrm{Al}}^{3+}$.
• The flocculating power for the coagulation of a positive sol is in the following order:
• For the coagulation of positive sol, the negative charge on ions must be high.

$[\mathrm{Fe}{\left(\mathrm{CN}\right)}_6{]}_4^{-}>{\mathrm{PO}}_4^{3-}>{\mathrm{SO}}_4^{2-}>{\mathrm{Cl}}^{-}$