Oxygen Demand, Chemical
Oxygen Demand, Chemical
OxygenCOD_Other_Other_MD3_Eng_Ody.fm Page 5 of 8
.
5. Place the vials in the
COD Reactor at 150 °C.
Digest for one hour.
6. Place the vials in a
cooling rack for two
minutes.
If the solution develops a
colorless upper layer and
a purple lower layer,
invert the vial several
times to mix and proceed
to the next step.
7. Cool the vials to room
temperature in a cool
water bath or with
running tap water for
several minutes.
8. Remove the vials
from the water and wipe
with a clean, dry paper
towel.
9. Touch
Hach Programs.
Select program
432 COD Mn III.
Touch
Start.
10. Install the 16-mm
adapter.
Note: See Section 2.6 in the
Instrument Manual for
installation details.
Place the blank into the
adapter.
11. Touch Zero.
The display will show:
0 mg/L COD Mn
12. Make sure the filter
disc is not suspended in
the middle of the vial; it
can interfere with the
instrument reading.
Note: The disc must be more
than 30 mm (1.2"), or less than
10 mm (0.4"), from the bottom
of the vial. Move it by gently
swirling, or by lightly tapping
the vial on the table top.
HRS MIN SECHRS MIN SEC
Hach Programs
Zero
1.2"
0.4"
YES YES NO
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