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DPD method.
| State | Liquid |
| Storage temp. | +15 / +25 ºC |
| Technique | DPD method |
PRINCIPLE
N,N-diethyl-p-phenylendiamine (DPD), reacts with FREE CHLORINE to produce a pink colour. In the same manner, BOUND CHLORINE, produces the same colour reaction when potassium iodide is added.
UTILITY
Disinfection of water (drinking, domestic use, swimming-pools...) by chlorination, promotes the production of diff erent chlorinated species. The contents in chlorine and hypochlorous acid is known as FREE CHLORINE. Chloramines are the main constituents of what is called BOUND CHLORINE. TOTAL CHLORINE, then, is the sum of the above two fractions. On the other hand, the use of pH monitoring allows the knowledge of which are the main constituents in the assayed water. Thus, at a pH value between 7.2 - 7.8, monochloramine concentration is higher than the one of trichloramine that shows a lower desinfecting power. Likewise, the FREE CHLORINE stability is higher. In swimming-pools, pH values under 7.0 can damage fi lters and other installations.