Page 44 - Statistics presented by Dr. Sara Ismail Aborass
P. 44

9/8/2023

    DETERMINATION :

    "Nessler's reagent method“

    Nessler’s reagent = K2HgI4 / KOH

                     (dipotassium tetraiodo- mercurate in alkaline solution)

    NH4+ + OH- → NH3 + H2O

    Saline           Free

    NH3 + 2 K2HgI4 + KOH → NH2Hg2I3 + 5 KI +
      H2O

     Free Nessler’s reagent yellowish

                                brown color

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               [B] NITRITE IN WATER :

                * SOURCES AND SIGNIFICANCE :
                ⚫ Nitrification

                  It originates from the decomposition of living materials. It is a
                  relatively toxic intermediate formed in the bacterial oxidation
                  of :
                  proteins → ammonium → nitrite → nitrate.
               Nitrite is oxidized during water treatment and should not be
                  detectable. Its presence indicates recent animal pollution.
                ⚫ Toxicity
                ⚫ Nitrite causes methaemoglobinaemia (cyanosis) (A condition in
                   which haemoglobin is converted to methaemoglobin that is
                   incapable of transpoting oxygen in the blood)

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