Social & Preventive Medicine Residual chlorine in chlorination of water should be- A 1 mg// after 1 hr B 0.5 mg/1 after 1 hr C 1 melt after 30 mins D 0.5 mg/1 after 30 mins 💡 Explanation Residual chlorine in chlorination of water should be- ✓ Correct Answer: B. 0.5 mg/1 after 1 hr