Hach DR/700 Procedures Manual page 118

NITROGEN, AMMONIA,
4.
Fill a 25-mL
sample cell to the
25-mL mark with
sample (the prepared
sample).
Note: For proof of
accuracy, use a 1.0 mg/L
Ammonia Nitrogen
Standard Solution (listed
under Optional
Reagents) in place of the
sample.
7.
Add three drops
of Polyvinyl Alcohol
Dispersing Agent to
each sample cell by
holding the dropping
bottle straight. Invert
several times to mix.
continued
5.
Fill another
25-mL sample cell
with demineralized
water (the blank).
Note: The demineralized
water and sample should
be at 20 ± 1°C (68 ±2°F)
for best results. Higher
temperatures cause high
results; lower
temperatures cause low
results.
8.
Pipet 1.0 mL of
Nessler Reagent to
each sample cell.
Cap and invert several
times to mix.
Note: Nessler Reagent
is toxic and corrosive.
Pipet carefully.
Note: A yellow color
will develop if ammonia
is present. The reagent
will cause a faint yellow
color in the blank.
42-34
6.
Add three drops
of Mineral Stabilizer
to each sample cell.
Cap and invert several
times to mix.
1 minute
9.
Wait 1 minute.
Note: Do not wait more
than five minutes after
Step 8 before
performing Step 13.