Hach AutoCAT 9000 Instruction Manual page 89

AutoCAT Titration Method
1.
Press the
CHECK MARK
to enter a new volume.
Press to confirm.
1
5.
Purge nitrogen gas
through the sample for
15 minutes.
When the timer beeps,
transfer the purged sample
into a 250-mL beaker. Add
the specified magnetic stir
bar.
Note: If the nitrogen purge has
already been performed, press
DEL to skip this timer and
proceed to the next step.
50081_Chlorine_ChlorineDioxide.fm
2.
Pipet 200 mL sample
into a Gas Washing Bottle
(GWB).
Add 1 mL of pH 7 Phosphate
buffer.
Swirl to mix.
6.
Use the measuring
spoon to add 1.0 g of
potassium iodide (KI).
Place the sample onto the
stirrer platform.
Press the
CHECK MARK
to confirm.
Note: KI is added in excess.
The precise amount added is
not crucial for the accuracy or
precision of the analysis.
Chlorine Dioxide Titr. 3
3.
Insert the purge tube
and dispersion tip into the
GWB. Connect the GWB
inlet to a tank of purified
nitrogen.
7.
The timer will start to
allow a short period of time
for the reagents to mix
before starting the titration.
Chlorine Dioxide
4.
Use a needle valve
to adjust the flow of
nitrogen to provide a steady
stream of bubbles through
the sample.
Press the
CHECK MARK
to continue.
8.
Lower the electrode
head onto the beaker rim.
Press the
CHECK MARK
to confirm.
Chlorine Dioxide
Page 87