The most effective coagulating agent for antimony sulphide sol is

• A

  $\mathrm{Na}_2 \mathrm{SO}_4$
• B

  $\mathrm{CaCl}_2$
• C

  $\mathrm{NH}_4 \mathrm{Cl}$
• Correct answer
  D

  $\mathrm{Al}_2\left(\mathrm{SO}_4\right)_3$

Hence, the correct answer is option: 'D'.