Hach AutoCAT 9000 - Sampling; 7.1 Chlorine Sample Considerations; 7.2 Container Pretreatment; 7.3 Sample Handling

Iodine
Iodine
50081_IodineCalibration.fm Page 61
Safety
Use good safety practices and laboratory techniques throughout the procedure. Consult
the Material Safety Data Sheet (MSDS) for specific reagent(s) information.
Summary of Method
The 0.0282 N Iodine solution is standardized by titrating it against 0.1000 N Arsenite
Standard Solution. The Iodine calibration procedure embedded in the AutoCAT 9000 is
adapted from procedure 4500-Cl C. g. in “Standard Methods for Examination of Water
and Wastewater” (20th Edition).
A calibration sample is prepared by adding 1.00 mL of standard 0.1000 N Arsenite
solution and 4.0 g sodium bicarbonate (NaHCO
3
) to 200 mL of chlorine free deionized
water. The calibration sample is then titrated against the Iodine titrant. The embedded
procedure calls for a 3.4-mL predose prior to titration. The titration end point is around
3.5 mL using the embedded method as defined. Perform a back titration to an
amperometric end point.
25. Press 1 to select New
Test to run a replicate
calibration. Proceed to
step 26 or select
Press
2 to select End
Analysis and store the titrant
calibration value and return
to the Methods menu.
Note: If subsequent replicate
calibrations are run, the final
titrant concentration will
automatically be stored as the
mean value from all the
replicate titrant calibrations.
26. The replicate analysis is
identical to the first
calibration.
Upon completion of the
analysis, and acceptance of
the data, subsequent replicate
analyses can be performed if
desired.
Press
1 to select Continue
and perform additional tests
and/or samples, or press
2 to
select More Details to view
analysis statistics for the
current calibration.
27. The arithmetic mean is
calculated from the replicate
analyses.
Press the
CHECK MARK to
accept the calibration value
and return to the
Titrants menu.
In the Titrants menu, the
accepted calibration has
caused the Titrant tab icon
to become sunny. This
indicates that the titrant
concentration has been
properly calibrated and
analyses may resume.