Hach DR/700 - Page 564

61-8
COBALT, continued
4. Measure 25 mL of
sample in a 25-mL
graduated mixing
cylinder (the prepared
sample).
Note: If sample is less
than 10
o
C (50
o
F),
warm to room
temperature prior to
analysis.
Note: For proof of
accuracy, use a 1.0 mg/L
cobalt standard solution
(preparation given in
Accuracy Check) in
place of the sample.
5. Measure 25 mL of
demineralized water
in a second 25-mL
cylinder (the blank).
6. Add the contents
of one Phthalate-
Phosphate Reagent
Powder Pillow to
each cylinder.
Stopper and
immediately shake to
dissolve.
Note: If sample contains
iron (Fe
3+
), it is
important that all of the
powder be dissolved
completely before
continuing with Step 7.
7. Add 1.0 mL of
0.3% PAN Indicator
Solution to each
cylinder. Stopper and
invert several times to
mix.
Note: Use plastic
dropper provide to add
PAN solution.
8. Wait 3 minutes.
Note: During color
development, the
sample solution color
may vary from green to
dark red, depending on
the chemical make-up of
the sample. The
demineralized water
blank should be yellow.
9. Add the contents
of one EDTA Reagent
Powder Pillow to
each cylinder.
Stopper and shake to
dissolve.
3 minutes