NH4Cl
Na2SO4
CaCl2
Al2(SO4)3
The correct option is C Al2(SO4)3
Sb2S3 is a negative sol. Al2(SO4)3 will be the most effective coagulant due to higher charge density on Al3+ by the Hardy-Schulze rule. According to the Hardy-Schulze rule, the greater the valency of the active ion, the greater will be its coagulating power.