Silica, Low Range Heteropoly Blue Method - Hach DR/850 Procedures Manual

SILICA, Low Range
Heteropoly Blue Method
1.
Enter the stored
program number for low
range silica (SiO ).
2
Press:
PRGM
The display will show:
PRGM ?
5.
Press:
TIMER ENTER
A 4-minute reaction
period will begin.
Note: Reaction time given
is for samples at 20 °C
(68 °F). If the sample
temperature is 10 °C
(50 °F), wait 8 minutes. If
the sample temperature is
30 °C (86 °F), wait
2 minutes.
* Adapted from Standard Methods for the Examination of Water and Wastewater.
(0 to 1.60 mg/L)
*
2.
Press:
90 ENTER
The display will show
mg/L, SiO2 and the
ZERO icon.
6.
After the timer
beeps, add the contents
of one Citric Acid
Reagent Powder Pillow
to each sample cell.
Swirl to mix.
3.
Fill two sample
cells to the 10-mL line
with sample.
7.
The display will
show:
1:00 TIMER 2
Press:
ENTER
A 1-minute reaction
period will begin.
Phosphate interference
is eliminated during
this period.
Note: The time given is for
samples at 20 °C (68 °F). If
the sample temperature is
10 °C (50 °F), wait two
minutes. If the sample is
30 °C (86 °F), wait
30 seconds.
393
Method 8186
For water and seawater
4.
Add 15 drops of
Molybdate 3 Reagent to
each sample cell. Swirl
to mix.
Note: For greatest
accuracy, hold dropping
bottle vertical.
8.
After the timer
beeps, add the contents
of one Amino Acid F
Reagent Powder Pillow
to one of the sample
cells (the prepared
sample). Invert to mix.
Note: The sample cell
without the Amino Acid F
Reagent is the blank.