Hach DR/700 Procedures Manual page 738

SILICA, LR,
4.
Fill a 10-mL cell
to the 10-mL line
with sample.
Note: A 25-mL sample
can be tested by using
25-mL sample cells and
the reagents listed under
Optional Reagents.
Note: For proof of
accuracy, use a 0.5 or
1.0 mg/L Silica
Standard Solution
(listed under Optional
Reagents) in place of
the sample.
7.
Add the contents
of one Citric Acid
Reagent Powder
Pillow to the sample
cell. Cap and invert
several times to mix.
This is the blank.
continued
5.
Add 10 drops of
Molybdate 3 Reagent
to the cell. Cap and
invert several times to
mix.
Note: If 25-mL cells are
used, add 0.5 mL of
Molybdate 3 Reagent
from the dropper
supplied with the 100-mL
bottle listed under
Optional Reagents.
1 minute
8.
Wait 1 minute.
Note: The one-minute
reaction period is for
samples at 20 °C (68
°F). If sample
temperature is at 10°C
(50 °F), wait two
minutes. If sample
temperature is at 30 °C
(86 °F), wait 30 sec.
81-64
4 minutes
6.
Wait 4 minutes
and remove cap.
Note: Reaction time
depends on sample
temperature. The time
given is for samples at
20 °C (68 °F). If sample
temperature is 10 °C
(50 °F), wait 8 minutes.
If at 30 °C
(86 °F), wait 2 minutes.
9.
Place the blank in
the cell holder
Note: In bright sunlight
it may be necessary to
close the cell
compartment cover.