DISCRETE ANALYZER CHEMISTRY Ammonia (NH 3 ) Method
Chemical Reactions Ammonium reacts with hypochlorite, formed by alkaline hydrolysis of sodium dichloroisocyanurate, and with salicylate at a pH of at least 12.6 in the presence of sodium nitroprusside as a catalyst. This produces a compound with a blue color (Indophenol). Citrate is used as a chelating reagent to eliminate interferences by cation such as calcium and magnesium. This method is is a common, safer variation to the to the chemistry of Berthelot’s reagent.
Step 1: Hypochlorite formed by alkaline hydrolysis of dichloroisocyanurate
Alkaline Hydrolysis
2 ClO -
Basic pH
Step 2: Ammonia reacts with hypochlorite to form chloramine
ClO - + NH 3
NH 2 Cl
Step 3: Chloramine reacts with salicylate to form indophenol
NH 2 Cl + 2
Note: Step 3 requires the loss of 2(CO 2 ) by decarboxylation.
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