WKS 276230 Manual De Instrucciones página 49

Methods
GB
Notes:
1. Temperature of the sample should be 15°C –25°C.
2. If Silica or Phosphate is present a yellow colour is developed.
3. In this step any yellow colour due to Phosphate is removed.
4. Substances who may interfere when present in concentrations at:
Substance
Iron
Phosphate
Sulfide
Occasionally water samples contain forms of silica which reacts very slowly with Molyb-
date. The nature of these forms is not known.
A pre-treatment with Sodium hydrogencarbonate and then with Sulfuric Acid will make
these forms reactive to Molybdate (pre-treatment is given in "Standard Methods for the
Examination of Water and Wastewater" under "Silica Digestion with Sodium Bicarbo-
nate").
5. Conversion:
mg/l Si = mg/l SiO
2
Reagent
Set
VARIO Silica HR Molybdate F10
VARIO Silica HR Acid Rgt F10
VARIO Silica HR Citric Acid F10
Interference
large amounts interfere
does not interfere at concentrations less than 50 mg/l PO
at 60 mg/l PO the interference is approx. – 2 %
4
at 75 mg/l PO the interference is approx. – 11 %
4
interferes at all levels
x 0.47
Form of reagent/Quantity
Powder Pack / 100
Powder Pack / 100
Powder Pack / 100
4
Order-No.
535700