Question

What change is necessary to update Hardy schulze rules?

Answer 1

Hardy schulze rule:

• “The greater the valency of the flocculating ion added, the greater is its power to cause precipitation. This is known as Hardy-Schulze rule.”
• The coagulating power increases with the valency of an ion.
• For example, in the coagulation of a negative sol, the order of flocculating power can be depicted as:

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

• Similarly, in the coagulation of a positive sol, the order of flocculating power can be depicted as:

$[\mathrm{Fe}{\left(\mathrm{CN}\right)}_6{]}^{4-}>{{\mathrm{PO}}_4}^{3-}>{{\mathrm{SO}}_4}^{2-}>{\mathrm{Cl}}^{–}$

Change to update Hardy schulze rule:

• This law can be changed in terms of polarising power instead of the valency of the flocculating ion which states that the greater the polarising power of flocculating ion, the greater its power to cause precipitation.