Hach DR/700 Procedures Manual page 646

SURFACTANTS, ANIONIC,
7.
Remove the
stopper from the
separatory funnel.
Drain the water layer
off the bottom and
discard it.
10.
Install module
number
61.01
in a DR/700.
8.
Fill a 25-mL cell
to the 25-mL line
with the top benzene
layer (the prepared
sample). Cap.
Note: The benzene
extract cannot be
filtered before color
measurement.
Filtration will remove
the color.
11.
Press:
I/O
The display will show
610 nm
and module number
61.01
61-90
continued
9.
Fill a 25-mL cell
to the 25-mL line
with pure benzene
(the blank). Cap.
12.
After 2 seconds,
the display will show
a program number,
the concentration
units, decimal
position, and zero
prompt. If necessary,
press the
UP ARROW
key until the lower
display shows
program number
61.13.1