Hach DR/700 - Page 738

81-64
SILICA, LR, continued
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.
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.
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.
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.
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.
9. Place the blank in
the cell holder
Note: In bright sunlight
it may be necessary to
close the cell
compartment cover.
4 minutes
1 minute