Hach DR/700 Procedures Manual page 380

CHLORINE, FREE,
Bromine, iodine, ozone and oxidized forms of manganese and chromium
also may react and show as chlorine. To compensate for the effects of
4+
manganese (Mn
above, then add 3 drops of potassium iodide, 30 g/L, to 25 mL of sample,
mix and wait 1 minute. Add 3 drops of sodium arsenite, 5 g/L, and mix.
Analyze this sample as described above. (If chromium is present, allow
exactly the same reaction period with the DPD for both analyses).
Subtract the result of this test from the original analysis to obtain the
accurate chlorine result.
DPD Free Chlorine Reagent Powder Pillows and AccuVac Ampuls
contain a buffer formulation which will withstand high (at least
1000 mg/L) levels of hardness without interference.
SUMMARY OF METHOD
Chlorine in the sample as hypochlorous acid or hypochlorite ion (free
chlorine or free available chlorine) immediately reacts with DPD (N,N-
diethyl-p-phenylenediamine) indicator to form a red color which is
proportional to the chlorine concentration.
REQUIRED REAGENTS (Using Powder Pillows)
Description
DPD Free Chlorine Reagent
Powder Pillows, 10 mL . . . . 1 pillow . . . . 100/pkg . . . . . . . 21055-69
REQUIRED REAGENTS (Using AccuVac Ampuls)
DPD Free Chlorine Reagent
AccuVac Ampuls . . . . . . . . 1 ampul . . . . 25/pkg . . . . . . . . 25020-25
REQUIRED APPARATUS (Using Powder Pillows)
Clippers, for opening
powder pillows . . . . . . . . . . 1 . . . . . . . . . each . . . . . . . . . . . . 968-00
DR/700 Filter Module
Number 52.01. . . . . . . . . . . 1 . . . . . . . . . each . . . . . . . . . . 46252-00
REQUIRED APPARATUS (Using AccuVac Ampuls)
Adapter, AccuVac vial. . . . . . . 1 . . . . . . . . . each . . . . . . . . . . 43784-00
Beaker, 50 mL . . . . . . . . . . . . 1 . . . . . . . . . each . . . . . . . . . . . . 500-41
DR/700 Filter Module
Number 52.01. . . . . . . . . . . 1 . . . . . . . . . each . . . . . . . . . . 46252-00
continued
) or chromium (Cr
Quantity
Per Test
6+
), adjust pH to 6 to 7 as described
Unit
52-54
Cat. No.