behr TRS 300
– 26 –
271005
behr TRS 300
– 27 –
© behr Labor-Technik 2007
271005
The COD program
The program for quantitation of Chemical Oxygen
Demand (COD) in accordance with DIN 38409,
Parts 41 and 42, is permanently programmed. It
can be found by selecting Program 00.
The standard specifies that the samples should
be heated to 148° C (the boiling point of the
water/sulfuric acid mixture) within 10 minutes and
should then be left to simmer for the remainder of
the total of two hours.
A heating temperature of 155° C has proven ade-
quate for keeping the samples simmering. Greater
heat is required to bring the samples to this boiling
temperature. For this reason, the COD program
firstly heats 20° C above the target temperature,
i.e., to 175° C. Insertion of the cold samples cau-
ses the temperature of the heating block to firstly
drop drastically, and the control unit will heat to
compensate for this. Boiling temperature is reach-
ed after around 6 minutes and the samples will
boil. The temperature boost switches off at this
point.
„155 + 20“ is shown on the display as the target
temperature during preheating and during the
six-minute starting phase.
155
Prog COD
175
°C
min
120
+20
120
