Hach AutoCAT 9000 Instruction Manual page 100

Free Chlorine
Safety
Summary of Method
Required Reagents
Description
Phenylarsine Oxide (PAO) Titrant, 0.00564 N............................................ varies................ 1000 mL ...............1999-53
Phosphate Buffer, pH 7, w/dropper ............................................................. 1 mL................. 100 mL ...............21553-32
Required Apparatus
Beaker, Glass, 250-mL ................................................................................ 1 ....................... each......................500-46H
Cylinder, Graduated, 250 mL ...................................................................... 1 ....................... each.........................508-46
Magnetic Stir Bar, Teflon
Optional Reagents
Chlorine Standard Solution, Voluette
Dilution water, organic-free ........................................................................ varies................ 500 mL ...............26415-49
Optional Apparatus
Mini-printer, thermal, w/cable............................................................................................... each.....................A70P021
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Page 98
Sample
Free Cl
Drinking Water Free Cl
Free Cl
Lower Limit
Titration curve end points are not as sharp as those for Total Chlorine. Therefore, the
determination of Free Chlorine concentrations below 0.1 mg/L becomes problematic. As
a result, the lower limit for the AutoCAT 9000 has been arbitrarily set to 0.1 mg/L for
experimental reasons.
Use good safety practices and laboratory techniques throughout the procedure. Consult
the Material Safety Data Sheet (MSDS) for specific reagent(s) information.
This procedure follows method number 4500-Cl D. b. in "Standard Methods for the
Examination of Water and Wastewater" (20th Edition). This procedure permits
determination of the Free Chlorine concentration in a water sample. Free chlorine
corresponds to that portion of chlorine existing either as elemental chlorine (Cl
hypochlorous acid (HOCl), or hypochlorite (OCl
In the procedure, the sample pH is adjusted to pH 7 by addition of Phosphate buffer. The
sample solution is then titrated amperometrically with standard phenylarsine oxide
solution.
®*
coated............................................................. 1 ....................... each.....................50085-00
®
Ampules, 10-mL ........................... varies................ 16/pkg.................14268-10
Call toll-free 800-227-4224
Contact the HACH office or distributor serving you.
www.hach.com ; E-mail –
Table 3 Accuracy Assessments
Spike Addition Average % Recovery
at 0.060 mg/L
2
at 0.220 mg/L
2
at 0.530 mg/L
2
–
Qty. required per test
techhelp@hach.com
% Range of
Recovery
92.6 (n=4) 87.5–98.0
89.7 (n=6) 89.2–92.7
91.0 (n=4) 85.4–93.5
) ion.
Unit
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WORLD HEADQUARTERS
Telephone: (970) 669-3050
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50081_Chlorine_Free_Forward.fm
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2
Cat. No.
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