Hach POCKET COLORIMETER II Instruction Manual page 34

Chlorine, Free and Total, HR,
4.
Press:
ZERO/SCROLL
The display will show
"- - - -" followed by "0.0".
Remove the blank.
continued
5.
Fill another 1-cm/10-mL
sample cell to the 5-mL line
with sample. Cap.
Do not use the same
Note:
sample cells for free and total
chlorine without thoroughly
rinsing the cells between the
free and total tests.
1—34
6.
Add the contents of two
DPD Free Chlorine or two
DPD Total Chlorine Powder
Pillows to the sample cell
(the prepared sample).
Cap the cell and shake gently
for 20 seconds.
Gentle shaking
Note:
dissipates bubbles which may
form in samples containing
dissolved gases.