Hach DR/700 Procedures Manual page 192

COLOR, TRUE AND APPARENT,
7.
After 2 seconds,
the display will show
a program number,
the concentration
units and the zero
prompt. If necessary,
press the
UP ARROW
key until the lower
display shows
program number
45.03.1
10.
Place the blank
in the cell holder.
Note: In bright light it
may be necessary to
close the cell
compartment cover.
8.
Pour about 50 mL
of sample through the
filter.
11.
Press:
ZERO
The display will
count down to 0.
Then the display will
show 0 Units PtCo
color and the zero
prompt will turn off.
45-20
continued
9.
Fill a second
10-mL cell to the
10-mL line with the
filtered sample (the
prepared sample).
Note: For proof of
accuracy, use a 250 unit
platinum-cobalt color
standard solution
(preparation given in
Accuracy Check) in
place of the filtered
sample.
12.
Place the
prepared sample in
the cell holder.
Note: In bright light it
may be necessary to
close the cell
compartment cover.