Hach DR/850 Procedures Manual page 348

PHOSPHORUS, REACTIVE,
5.
Press:
TIMER ENTER
A two-minute reaction
period will begin.
Perform Steps 6-8
during this period.
Note: If the acid-persulfate
digestion was used, an 8-10
minute reaction period is
required.
9.
After the timer
beeps, place the
prepared sample into the
cell holder. Tightly
cover the sample cell
with the instrument cap.
continued
6.
Fill another sample
cell with 10 mL of
sample (the blank).
10.
Press:
READ
The cursor will move to
the right, then the result
in mg/L phosphate
3-
(PO ) will be
4
displayed.
Note: Standard Adjust may
be performed using a
3-
2.0-mg/L PO standard;
4
see Section 1.
7.
Place the blank into
the cell holder. Tightly
cover the sample cell
with the instrument cap.
348
8.
Press:
ZERO
The cursor will move to
the right, then the
display will show:
0.00 mg/L PO4
Note: If Reagent Blank
Correction is on, the
display may flash "limit".
See Section 1.