COD,
High Range
COD3 Plus Colorimeter 10.16
APPLICATION:
Domestic and industrial wastes.
RANGE:
0–15000 mg/L COD
MDL:
500 mg/L
METHOD:
Dichromate in the presence of silver salts, at high
temperature in a closed system, oxidizes most organic
compounds to 95-100% of the theoretical amount. This
process is called digestion. As dichromate oxidizes the
organic compounds, a green complex is formed. The
concentration of the green complex is measured at 605 nm
and is directly proportional to the COD of the sample.
SAMPLE HANDLING &
RESERVATION:
Collect samples in glass and test as soon as possible. If
samples must be stored, preservation is accomplished by
the addition of concentrated H2SO4 to adjust the pH below
2. Samples with suspended solids should be homogenized
in a blender (100 mL for 30 seconds) and then stirred gently
with a magnetic stirrer.
INTERFERENCES:
Volatile organic compounds are not oxidized to the extent
that they are in the vapor above the digestion solution.
Therefore, they do not contribute to the COD reading.
Contains mercury sulfate to prevent interference from
chloride. Nitrite gives a positive interference of 1.1 ppm
O
2
per ppm NO
2
–N, which is insignifi cant unless nitrite
concentrations are very high. Other reduced inorganic
compounds are stoichiometrically oxidized, causing
a positive interference. Corrections can be made for
these compounds based upon their stoichiometry and
concentrations.
When scanning samples in 16 mm tubes, such as COD, the
sample chamber lid can not be closed. Use the COD adapter
to minimize stray light interference. To further reduce stray
light interference, do not Scan Sample in direct sunlight.
Testing
Содержание COD3 Plus
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