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Silica
5.
Touch the timer icon.
Touch
.
OK
A ten-minute reaction
period will begin.
10 mL
9.
Place the blank into
the cell holder.
Interferences
Interfering Substance
Color
Iron
Phosphate
2–
Sulfides (S
)
Turbidity
Silica
Page 2 of 4
6.
When the timer
beeps, add the contents of
one Citric Acid Powder
Pillow to the sample cell.
Swirl to mix.
Any yellow color due to
phosphorus is removed in
this step.
Zero
10.
Touch
.
Zero
The display will show:
0.0 mg/L SiO
2
Eliminated by zeroing the instrument with the original sample.
2+
3+
High levels of Fe
and Fe
Does not interfere below 50 mg/L PO
3–
At 75 mg/L PO
, the interference is negative 11%.
4
All levels interfere.
Eliminated by zeroing the instrument with the original sample.
Occasionally a sample contains silica which reacts very slowly with molybdate.
The nature of these "molybdate-unreactive" forms is not known. A pretreatment
with Sodium Bicarbonate (Cat. No. 776-01), then Sulfuric Acid (Cat. No. 1270-32)
will make these forms reactive to molybdate. The pretreatment is given in
7.
Touch the timer icon.
Touch
.
OK
A two-minute reaction
period will begin.
Perform step 8–step 11
within three minutes after
the timer beeps.
10 mL
11.
Place the prepared
sample into the cell
holder.
Interference Levels and Treatments
interfere.
3–
. At 60 mg/L PO
4
4
8.
Fill a second sample
cell with 10 mL of the
original sample (the
blank).
Read
12.
Touch
.
Read
Results will appear in
mg/L SiO
.
2
3–
, a negative 2% interference occurs.
Silica_PP_High_SLM_Eng_Ody.fm
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