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# What is the hardy Schulze rule?

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## 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. $\left[\mathrm{Fe}{\left(\mathrm{CN}\right)}_{6}{\right]}_{4}^{-}>{\mathrm{PO}}_{4}^{3-}>{\mathrm{SO}}_{4}^{2-}>{\mathrm{Cl}}^{-}$

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