LaMotte DPD-FAS TITRIMETRIC OUT FIT DT User Manual
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E. INTERFERENCE
The only interference in chlorine testing is the possibility of oxidized
manganese in the water. This can be tested as follows:
1.
Use the 1.0 g spoon (0697) to add two *Potassium Iodide Crystals
(6810) to a clean 250 mL Erlenmeyer flask (0433).
2.
Use the 100 mL graduated cylinder (0419) to add 100 mL of sample
water to the flask (0433). Swirl to mix.
3.
Use the 0.5 mL pipet (0369) to add 0.5 mL of *Sodium Arsenite
Solution (4128).
4.
Use the 0.5 g spoon to add 0.5 g of *DPD #1 (6807) Powder. Swirl
until reagents are dissolved. If oxidized manganese is present,
solution will turn pink.
5.
Titrate rapidly with the diluted Ferrous Ammonium Sulfate Solution
in the buret until the pink color disappears. Record buret reading.
Subtract this reading from the previous test readings.
III.DPD METHOD FOR CHLORINE DIOXIDE AND CHLORITE
This method is an extension of the standard DPD method for
determining free chlorine and chloramines in water.
NOTE:
Titration should be carried out as rapidly as possible ignoring
any color driftback at endpoints.
A. CHLORINE DIOXIDE USING *STEADIFAC REAGENT
1.
Use the 1.0 mL pipet (0354) to add 2 mL of Glycine Solution
(6811) to a 100 mL sample. Mix.
2.
Use the 0.5 g spoon (0698) to add 0.5 g of *DPD #1 Powder (6807)
to the sample.
3.
Use the 0.25 g spoon (0695) to add 0.25 g of *EDTA Disodium Salt
(6382). Mix.
4.
Add 10 drops of *Steadifac Reagent (6383WT). Mix.
5.
Titrate rapidly with the diluted Ferrous Ammonium Sulfate
Solution. This is Reading G1.
NOTE:
To obtain chlorine dioxide in terms of mg/L ClO
2
, multiply
the G1 reading by 1.9 instead of 5.
B. CHLORINE DIOXIDE WITHOUT *STEADIFAC REAGENT
1.
Use a second 100 mL sample to follow procedures of Steps 1 through
3 above.
2.
Titrate rapidly with the diluted Ferrous Ammonium Sulfate
Solution. This is Reading G2.
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