POISON. Alkali. Contains mercury compounds and sodium hydroxide. Contact may cause
burns and irritation. Do not ingest or allow contact with skin or eyes. In case of contact,
immediately flush eyes and skin with water for 15 minutes. Remove contaminated clothing. In
case of ingestion, DO NOT induce vomiting. Give 1 to 2 glasses of water. Give at least one
ounce of vinegar in an equal amount of water. Call medic in all cases.
Use the 1.0 ml pipet(5, fig. 1-1) and the pipet filler(27) to transfer 1.0 ml of Nessler reagent(17) to both
sample cells(7, fig. 2-5).
If the Nessler reagent becomes dark brown it should be replaced.
A precipitate in the bottom of the Nessler reagent bottle is normal. However, carefully extract
reagent from the bottle without stirring up any of the solid material at the bottom. If any solid
material from the Nessler reagent is used, the results will be erratic.
Wait at least 10 minutes but not more than 25 minutes. A yellow color will develop if ammonia nitrogen is
Iron and sulfides will interfere by causing a turbidity with the Nessler reagent. Less common
interferences such as hydrazine, and several organic compounds may cause turbidity, or a tint of
green or other colors in the treated sample. If such interference occurs this test method may not
be suitable for the water sample.
Place the sample cell(7) containing the treated deionized water solution into the spectrophotometer cell
holder well(5) (as a blank). Put the "Nitrogen Ammonia (Nessler Method)" meter scale card(2) into the
meter. Adjust the wavelength dial(8) to 425 nm. Turn the LIGHT CONTROL knob(l0) until the meter
scale(14) reads 0 mg/l.
Remove the blank cell (deionized water) and place the treated test sample in the spectrophotometer cell
holder(5). Read the results on the meter scale(14).
Interpretation of Results:
The results indicated by the meter scale are in mg/l of nitrogen.
The concentration of ammonia (NH3) in mg/1 may be computed by multiplying the concentration of
nitrogen read from the meter scale by 1.22.
The concentration of ammonium ions (NH4) in mg/l may be computed by multiplying the concentration of
nitrogen read from the meter scale by 1.29.
Refer to para 2.6.2 for shut down of the Spectrophotometer.