Question

For \( \text{As}_2\text{S}_3 \) sol, the most effective coagulating agent is:

• A. \( \text{CaCO}_3 \)
• B. \( \text{NaCl} \)
• C. \( \text{FeCl}_3 \)
• D. \( Clay \)

Hint:

The coagulation efficiency increases with the charge of the ion, following the Hardy-Schulze rule, which states that higher charges cause more effective coagulation.