Amoung NaCl, `Na_(2)SO_(4)` , `Na_(3)PO_(4)` electrolytes , `Na_(3)PO_(4)` which is more effective for coagulation of hydrated ferric oxide sol and why ?

Explanation

Amoung NaCl, `Na_(2)SO_(4), Na_(3)PO_(4)` electrolytes `Na_(3)PO_(4)` is more effective for coagulation of hydrated ferric oxide sol. This is explained by Hardy-Schulze rule.
`to` Greater the valence of the coagulating ion added, the greater is its power to cause coagulation. This is known as Hardy-Schulze rule.
`to` Coagulation ability order of the anions in the above salts is
`PO_(4)^(-3) gt SO_(4)^(-2) gt Cl^(-)`.