Hach AutoCAT 9000 - Page 94

Chlorine Dioxide
© Hach Company, 2002–2003, 2007. All rights reserved. Printed in the U.S.A. 3/07 3ed
Page 92 50081_Chlorine_ChlorineDioxide.fm
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Summary of Method
This procedure permits the determination of chlorine dioxide (ClO
2
), chlorite (ClO
2
–
),
and chlorine (Cl
2
) in the sample.
This is a multi-step procedure involving four amperometric titrations and two titration
samples. These titrations are as follows:
Sample 1
Sample 2
The AutoCAT 9000 stores all titration results and, after completion, calculates each
analyte value.
This method can be greatly accelerated by purging a sample portion (used for
Titrations 3 and 4) with nitrogen while performing titrations 1 and 2.
Required Reagents
Description Qty. required per test Unit Cat. No.
Phenylarsine Oxide (PAO) Titrant, 0.00564 N............................................varies................ 1000 mL ...............1999-53
Hydrochloric Acid Standard Solution, 2.5 N ..............................................4 mL................. 100 mL .................1418-32
Phosphate Buffer pH 7, w/dropper..............................................................2 mL................. 100 mL ...............21553-32
Potassium Iodide, ACS................................................................................2.0 g ................. 100 g....................167-26H
Required Apparatus
Description Qty. required per test Unit Cat. No.
Beaker, Glass, 250-mL ................................................................................1 ....................... each......................500-46H
Gas Washing Bottle .....................................................................................1 ....................... each.....................26622-00
Magnetic Stir Bar, Teflon
®*
coated.............................................................1 ....................... each.....................50085-00
Measuring Spoon, 1.0-g (NaCl weight), molded plastic.............................1 ....................... each.........................510-00
Pipet, Volumetric, Class A, 100-mL............................................................1 ....................... each.....................14515-42
Support, Ring Stand.....................................................................................1 ....................... each.........................563-00
Support Ring, for GWB...............................................................................1 ....................... each.....................26563-00
Optional Reagents
Dilution water, organic-free ........................................................................ varies................ 500 mL ...............26415-49
Optional Apparatus
Mini-printer, thermal, w/cable............................................................................................... each.....................A70P021
Cylinder, Graduated, 250 mL ......................................................................1 ....................... each.........................508-46
Titration 1 Cl
2
1
5
---
ClO
2
+→
Titration 2
4
5
---
ClO
2
ClO
2
–
+→
Titration 3 Cl
2
(not volatized by a nitrogen gas purge
)
→
Titration 4 ClO
2
–
→
*Teflon is a Registered Trademark of EI DuPont Company.