Hach DR/700 Procedures Manual page 328

ALUMINUM,
4.
Fill a 25-mL cell
to the 25-mL line
with the mixture (the
prepared sample).
Cap.
continued
5.
Add the contents
of one Bleaching 3
Reagent Powder
Pillow to the
remaining 25 mL in
the graduated mixing
cylinder. Stopper and
shake vigorously for
30 seconds (the
blank).
Note: This solution
should turn a light to
medium orange upon
bleaching. It will not
become colorless.
52-2
6.
Pour the
remaining 25 mL of
bleached sample in
the cylinder into a
second 25-mL sample
cell.