Hach sension6, Instruction Manual, Page: 48 / 86

47
SECTION 3,
continued
3.5 Using the BOD Accessory Kit
The optional BOD Accessory Kit, which includes an overflow
funnel with a built-in stirring bar, serves three purposes:
•
The kit eliminates the retrieval of magnetic stirring bars from
BOD sample bottles.
•
The funnel provides an overflow reservoir to hold sample
displaced when the DO probe is inserted in the bottle. This
permits the measurement to be made without spilling the
sample. When the DO probe is withdrawn, the displaced
solution can drain back into the bottle.
•
The funnel is designed to act as an electrode holder. This kit
is designed for use with Hach Model 51850 DO probe only.
3.6 Making BOD Determinations
Use the Hach BOD Accessory Kit with a magnetic stir plate and a
standard 300-mL BOD bottle.
1. Fill a standard 300-mL BOD bottle with the water sample and
insert the overflow funnel.
2. Insert the DO probe into the funnel and bottle.
3. Place the BOD bottle on a magnetic stirrer so that the probe is
over the center of the stir plate.
4. Start the magnetic stirrer and increase the speed until the
rotor loses its cycle. Adjust until the rotor regains its cycle
and mark this point on the speed scale of the stirrer. This
identifies the optimum working point. Insufficient stirring
will cause erroneously low readings.
Note: If air bubbles develop below or on the probe membrane, allow the
stirrer about five seconds to remove, or hold the probe at a slight
angle and tap gently.