Hach DR/850, Procedures Manual, Page: 232 / 460

232
Summary of Method
Monochloramine (NH
2
Cl) and “free ammonia” (NH
3
and NH
4
+
)
can exist in the same water sample. Added hypochlorite combines
with free ammonia to form more monochloramine. In the presence
of a cyanoferrate catalyst, monochloramine in the sample reacts
with a substituted phenol to form an intermediate monoimine
compound. The intermediate couples with excess substituted phenol
to form a green-colored indophenol, which is proportional to the
amount of monochloramine present in the sample. Free ammonia is
determined by comparing the color intensities, with and without
added hypochlorite.
Safety
Good safety habits and laboratory techniques should be used
throughout the procedure. Consult the Material Safety Data Sheet
(MSDS) for information specific to the reagent used.
REQUIRED REAGENTS
Quantity Required
Description Per Test Unit Cat. No.
Free Ammonia Reagent Set (50 tests)
Includes: (1) 28022-99, (1) 28773-36................................................. 28797-00
Free Ammonia Reagent Solution........................................1 drop4 mL SCDB ........... 28773-36
Monochlor F Reagent Pillows ..........................................2 pillows100/pkg................ 28022-99
REQUIRED APPARATUS
Sample Cell, 1-cm/10-mL, with cap....................................... 2 ........ 2/pkg ................ 48643-02
OPTIONAL REAGENTS
Buffer, pH 8.3, Powder Pillows ....................................................... 25/pkg .................... 898-68
Chlorine Solution, Voluette
®
Ampule ............................................. 16/pkg ................ 14268-10
Hardness Treatment Reagent Pillows (1 per test)............................ 50/pkg ................ 28823-46
Nitrogen Ammonia Standard Solution, 10 mg/L as NH
3
–N .......... 500 mL .................... 153-49
Nitrogen Ammonia Standard Ampule,
50 mg/L as NH
3
–N, 10 mL.............................................................. 16/pkg ................ 14791-10
Nitrogen Ammonia Standard Solution, 100 mg/L as NH
3
–N ........ 500 mL ................ 24065-10
Nitrogen, Free Ammonia and Chloramine (Mono), continued