Hach AutoCAT 9000, Instruction Manual

Page: 131 / 176

Chlorite
Chlorite
50081_Chlorite.fm
Page 129
9.
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.
10.
Purge nitrogen gas
through the sample for 15
minutes.
When the timer beeps, move
to step 11.
Note: If the nitrogen purge has
already been performed, press
DEL to skip this timer and
proceed to the next step.
11.
Transfer the purged
sample into a 250-mL
beaker. Add the specified
magnetic stir bar.
All containers must be
pretreated for chlorine
demand, see Container
Pretreatment on page 61.
12.
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.
13.
The timer will start.
This allows a short period of
time for the reagents to mix
before starting the titration.
14.
Lower the electrode
head onto the beaker rim.
Press the
CHECK MARK
to
confirm.
15.
The analysis parameters
that have been stored for the
current Sub-ID may be
edited at this time.
Highlight the appropriate
line and press the
CHECK MARK
to change one
of the analysis parameters or
press
1
to confirm.
Note: Any changes made will
become the new default
parameters for this method
Sub-ID.
Note: These Sub-ID
parameters can be edited here
as 'run-time' settings, or from
the Main Menu as described in
Section 3.5.
16.
The Zoom Range
Determination window will
display the titration curve.
Use the navigation buttons to
select and move the cursors
to define the range of data
points for the analysis.
Note: Defining the range of
data points excludes
undesirable portions of the
titration curve from the
analysis.