Hach DR/850 Procedures Manual page 148

CHLORINE DIOXIDE,
5.
Press:
ZERO
The cursor will move to
the right, then the
display will show:
0.00 mg/L ClO2
Note: If Reagent Blank
Correction is on, the display
"limit"
may flash . See
Section 1 of the DR/800
Procedures Manual.
9.
Press:
READ
The cursor will move to
the right, then the result
in mg/L chlorine dioxide
will be displayed.
continued
6.
Add four drops of
Glycine Reagent to the
sample cell. Swirl to
mix.
Note: If the sample
temporarily turns yellow
after reagent addition, or the
"limit"
display flashes , it is
due to high chlorine dioxide
levels. Dilute a fresh sample
with chlorine dioxide-free
water and repeat the test. A
slight loss of chlorine dioxide
may occur during dilution.
Multiply the result by the
dilution factor.
7.
Add the contents of
one DPD Free Chlorine
Powder Pillow to the
sample cell (the
prepared sample). Cap
the cell and swirl to mix.
Note: A pink color will
develop if free chlorine
dioxide is present.
Note: Perform step 9 within
one minute of reagent
addition.
148
8.
Allow 30 seconds
for undissolved powder
to settle. Place the
prepared sample into the
cell holder. Tightly
cover the sample cell
with the instrument cap.
Note: Wipe off any liquid or
fingerprints before inserting
the sample cell into the
instrument.