Hach DR/700 Procedures Manual page 389

CHLORINE, TOTAL, continued
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 Total 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 can be present in water as free available chlorine and as
combined available chlorine. Both forms can exist in the same water
and be determined together as the total available chlorine. Free chlorine
is present as hypochlorous acid and/or hypochlorite ion. Combined
chlorine exists as monochloramine, dichloramine, nitrogen trichloride
and other chloro derivatives. The combined chlorine oxidizes iodide in
the reagent to iodine. The iodine reacts with DPD (N, N-diethyl-p-
phenylenediamine) along with free chlorine present in the sample to
form a red color which is proportional to the total chlorine
concentration. To determine the concentration of combined chlorine,
run a free chlorine test. Subtract the results from the results of the total
chlorine test to obtain combined chlorine.
REQUIRED REAGENTS (Using Powder Pillows)
Description
DPD Total Chlorine Reagent
Powder Pillows. . . . . . . . . . 1 pillow . . . 100/pkg . . . . . . . 21056-69
REQUIRED REAGENTS (Using AccuVac Ampuls)
DPD Total Chlorine Reagent
AccuVac Ampuls . . . . . . . . 1 ampul . . . . 25/pkg . . . . . . . . 25030-25
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
Quantity
Per Test Unit
52-63
Cat. No.