Hach DR/850, Procedures Manual, Page: 103 / 460

103
•
A common error in testing for chlorine is failure to obtain a
representative sample. If sampling from a tap, let the water
flow for at least five minutes to ensure a representative
sample. Let the sample container overflow with sample
several times. Cap the container so there is no air above the
sample.
•
If sampling with a sample cell, rinse the cell several times
with the sample, then carefully fill to the 5-mL mark. Proceed
with the chlorine test immediately.
Accuracy Check
1. Fill three mixing cylinders (Cat. No. 20886-38) with 5-mL
of sample.
2. Snap the neck of a HR Chlorine Ampule Standard, 50–
75 mg/L Cl
2
. Using the TenSette
®
Pipet, add 0.1 mL, 0.2 mL,
and 0.3 mL of standard, respectively, to each cylinder and
mix thoroughly.
3. Analyze each standard addition sample as described in the
procedure. Record each result.
4. Calculate the concentration of mg/L chlorine added to each
sample.
The spiked sample results should reflect the analyzed sample
result plus the calculated mg/L Cl
2
added to each sample. If these
increases do not occur, see Standard Additions in Section 1 of a
DR/800 Procedure Manual for more information.
mg/L chlorine added
volume of standard added label value of Cl
×
2
standard ampule
sample volume volume of standard added +
------------------------------------------------------------------------------------------------------------------------------------------------------- =
CHLORINE, FREE, Ultra-high Range, continued