Hach DR/700 Procedures Manual page 146

PHOSPHORUS, REACTIVE,
3 minutes
7.
Wait 3 minutes.
Note: If the sample
concentration is greater
than 24 mg/L, read at
exactly 3 minutes or
make a 1:1 dilution.
8.
Place the blank in
the cell holder.
Note: Typical indoor
lighting permits the
DR/700 to operate with
the cell compartment
cover open. In bright
sunlight, it may be
necessary to close the
cell compartment cover.
Transfer 10 mL of the
blank solution to a 10-
mL cell. If the
10-mL cell is used for
the blank, another
10-mL cell must be used
for the sample.
42-62
continued
9.
Press:
ZERO
The display will
count down to 0.
Then the display will
show 0.00 mg/L and
the zero prompt will
turn off.