Among the electrolysis of Na₂SO₄, CaCl₂, Al₂(SO₄)₃ and NH₄Cl, the most effective coagulating agent for Sb₂S₃ sol is

Sb₂S₃ sol is a negative sol

A negative sol is coagulated by a cation,according to Hardy-schulze rule

Coagulating power of electrolyte $\infty$ valency of the ion possessing opposite charge to that sol

Sb₂S₃ is most effectively coagulated by Al⁺³

Coagulating power of Al⁺³> Ca⁺²>Na⁺ for a negative sol