A public health engineer is asked to determine the exact dose of bleaching powder required to disinfect a newly dug well before it is commissioned. Which instrument is specifically designed to estimate the chlorine demand of water?
- A Jackson candle turbidimeter
- B Berkefeld filter
- C Horrock's apparatus ✓
- D Nessler's comparator
Correct answer: C. Horrock's apparatus
Explanation
Horrock's apparatus is a simple device used to determine the chlorine demand of water, that is, the amount of chlorine needed to leave an adequate free residual after a fixed contact time. It is routinely used for well disinfection in field conditions. Berkefeld is a filter, the candle turbidimeter measures turbidity, and Nessler's reagent tests ammonia, none of which estimate chlorine demand.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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