Hach DR/700 - Page 709

81-35
PHOSPHORUS, TOTAL, continued
10. Carefully
remove the vial from
the reactor. Place it
in a test tube rack and
allow to cool to room
temperature.
11. Remove the cap
from the vial. Add
2 mL of 1.00 N
sodium hydroxide to
the vial.
Note: A 2-mL Repipet
and 900-mL bottle of
NaOH can be used for
convenience when
analyzing multiple
samples.
12. Cap tightly and
shake to mix.
13. Fully insert a
COD Vial Adapter
into the cell holder
with the tabs in the
square slot.
14. Clean the
outside of the vial
with a towel. Place
the sample vial in the
adapter with the Hach
logo facing the front
of the instrument.
Note: Wiping with a
damp towel, followed by
a dry one, will remove
fingerprints or other
marks.
15. Press: ZERO
The display will
count down to 0.
Then the display will
show 0.0 mg/L, and
the zero prompt will
turn off.
Note: For multiple
samples, zero on the
first sample and record
the blank value.
Subtract the blank value
from each sample result.