Hach DR/850 Procedures Manual page 244

NITRATE, Low Range,
5.
Press:
TIMER ENTER
A 3-minute reaction
period will begin. Shake
the cylinder vigorously
throughout this three
minute period.
Note: Shaking time and
technique influence color
development. For most
accurate results, analyze a
standard solution several
times and adjust the
shaking time to obtain the
correct result.
9.
The display will
show: 15:00 TIMER 3
Press:
ENTER
A 15-minute reaction
period will begin.
Fill another sample cell
(the blank) with 10 mL
of sample.
continued
6.
When the timer
beeps, the display will
show: 2:00 TIMER 2
Press:
ENTER
A 2-minute reaction
period will begin.
Note: A deposit will remain
after the powder dissolves
and will not affect results.
10.
When the timer
beeps, place the blank
into the cell holder.
Tightly cover the sample
cell with the
instrument cap.
7.
When the timer
beeps, pour 10 mL of the
sample into a
sample cell.
Note: Do not transfer any
cadmium particles.
11.
Press:
ZERO
The cursor will move to
the right, then the
display will show:
0.00 mg/L NO3-N
Note: If Reagent Blank
Correction is on, the
display may flash "limit".
See Section 1.
244
8.
Add the contents of
one NitriVer 3 Nitrite
Reagent Powder Pillow
to the sample cell (the
prepared sample). Cap
the cell and shake gently
for 30 seconds.
Note: A pink color will
form if nitrate is present.
12.
Place the prepared
sample into the cell
holder. Tightly cover the
sample cell with the
instrument cap.