Why does the container need sodium thiosulfate in it?

Why does the container need sodium thiosulfate in it?

• A. To adjust pH
• B. To dechlorinate the sample
• C. To preserve chlorine residuals
• D. To sterilize the sample

Answer: (B)

Sodium thiosulfate is used to dechlorinate the sample. After collection, chlorine in the water can continue to react, altering test results. Adding thiosulfate neutralizes the chlorine (reacts with hypochlorous acid and hypochlorite), stopping any further disinfection and preserving the sample for accurate analysis. The other options don’t fit because pH adjustment uses acids or bases, preserving chlorine residuals would mean keeping the chlorine active (not neutralizing it), and sterilizing would require a sterilizing agent, not thiosulfate.

Sodium thiosulfate is used to dechlorinate the sample. After collection, chlorine in the water can continue to react, altering test results. Adding thiosulfate neutralizes the chlorine (reacts with hypochlorous acid and hypochlorite), stopping any further disinfection and preserving the sample for accurate analysis. The other options don’t fit because pH adjustment uses acids or bases, preserving chlorine residuals would mean keeping the chlorine active (not neutralizing it), and sterilizing would require a sterilizing agent, not thiosulfate.