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Reagents:
Carrier:
DI Water. The quality of the DI water
should be watched, since silica is often
encountered as a contaminant in water.
Silica contamination typically appears
as the filters on the DI apparatus
approach the end of their life cycle.
1-Liter Degassed DI Water.
Reagent 1: Indicator
solution.
250 mL of
0.02 M Ammonium Molybdate solution.
750 mL Degassed DI Water.
A volume
of ~1 M Hydrochloric Acid corresponding
to 0.33 mol acid equivalents. For
example, 330 mL of 1.000 N HCl, or 333
mL of 0.990 N HCl.
0.02 M Ammonium Molybdate
solution:
25.0 grams Ammonium molybdate
tetra-hydrate [1235.81 FW]. Dissolve in
water under gentle warming and dilute to
250 mL. Filter. Make sure the filter is
free of silica (do not use glass
filters). Adjust pH to 7-8 with
silica-free NaOH (approx. 7-8 mL of 50%
NaOH). Store in a plastic container.
Reagent 2: Phosphate
Suppressant solution.
250 mL of
0.15 M Oxalic Acid solution.
750 mL Degassed DI Water.
0.15 M Oxalic Acid solution:
18.75 grams Oxalic acid dihydrate
[126.07 FW]. Dissolve in water and
dilute to 250 mL. Store in a plastic
container.
Standards:
500ml
S65142-500 (Silica standard)
Source:
727-524-7732
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www.exaxol.com
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