Physical Chemical Operator SC Practice Test

DPD is a method of measuring what in water?

Nessler method DPD Amperometric Iodometric

Correct Answer:

DPD

Explanation:

Chlorine residual in water is measured with the DPD colorimetric method. The reagent N,N-diethyl-p-phenylenediamine reacts with chlorine species (like Cl2, HOCl, and OCl−) to form a pink compound, and the color intensity is proportional to the chlorine concentration. A colorimeter or color chart converts that shade into a chlorine value, commonly used for both free chlorine and total chlorine analyses. This makes DPD specifically a chlorine-measuring method, unlike Nessler (ammonia), amperometric (general electrochemical sensing), or iodometric (t titration-type) methods.

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