LaMotte DPD-FAS TITRIMETRIC OUT FIT DT - Manual (Page 10)

3. Titrate rapidly with the diluted Ferrous Ammonium Sulfate Solution
in the buret until the pink color disappears. Record buret reading as
Reading A.
Reading A – BR (mL) = (ppm) Free Chlorine
Retain sample and buret for testing Monochloramine.
D. MONOCHLORAMINE
4.
Use the 1.0 g spoon (0697) to add one small *Potassium Iodide
Crystal (6809) to the sample from Step 3. Swirl to mix. If
monochloramine is present, solution will turn pink.
5. Continue titrating with the diluted Ferrous Ammonium Sulfate
Solution until the pink color disappears. Record buret reading as
Reading B.
(Reading B – Reading A), mL = (ppm) Monochloramine
Retain sample and buret for testing Dichloramine.
E. DICHLORAMINE
6.
Use the 1.0 g spoon (0697) to add 1.0 g of *Potassium Iodide
Crystals (6809) to the sample from Step 5. Swirl until crystals are
dissolved. Wait 2 minutes. If Dichloramine is present, solution will
turn pink.
7. Continue titrating with the diluted Ferrous Ammonium Sulfate
Solution until the pink color disappears. Record buret reading as
Reading C.
NOTE:
For 100 mL sample, 1 mL FAS solution equals 1 mg/L
(ppm) Chlorine.
Calculations
Bromine = BR
Free Chlorine = A – BR
Monochloramine = B – A
Dichloramine = C – B
Combined Chlorine = C – A
V. DPD METHOD FOR IODINE
Iodine reacts with DPD in the same manner as Free Chlorine so that it
is necessary only to perform the procedure for Free Chlorine. DPD
methods for differentiating free iodine from free chlorine and
chloramines have not been developed. For a 100 mL sample, 1 mL FAS
solution equals 1 mg/L (ppm) available chlorine. If it is desired to report
in terms of iodine, multiply the result by 3.6.
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