Which method is used to measure chlorine residuals?

Which method is used to measure chlorine residuals?

• A. Amperometric titration
• B. DPD method (colorimetric)
• C. pH indicator method
• D. Titration with iodide

Answer: (B)

Measuring chlorine residuals is done with the colorimetric DPD method. In this test, chlorine in the water oxidizes the DPD reagent, producing a pink color. The color’s intensity is proportional to the chlorine concentration, so you can read the residual level using a color chart or a photometer. This approach is preferred because it gives a direct, quick, and easy measurement of how much chlorine remains, which is exactly what needs to be monitored after disinfection. Other methods either require more complex equipment or don’t provide a straightforward readout for chlorine residuals.

Measuring chlorine residuals is done with the colorimetric DPD method. In this test, chlorine in the water oxidizes the DPD reagent, producing a pink color. The color’s intensity is proportional to the chlorine concentration, so you can read the residual level using a color chart or a photometer. This approach is preferred because it gives a direct, quick, and easy measurement of how much chlorine remains, which is exactly what needs to be monitored after disinfection. Other methods either require more complex equipment or don’t provide a straightforward readout for chlorine residuals.