Hach DR/850, Procedures Manual, Page: 226 / 460

226
9.
Cap the reagent
bottle to maintain
reagent performance and
stability.
10.
Cap the cell and
mix.
Note: If the sample
becomes cloudy by the end
of the reaction period,
pretreat the sample and
retest. See Interferences on
page 228.
11.
Press:
TIMER ENTER
A five-minute reaction
period will begin.
Note: The color
development time depends
on the sample temperature.
See Table 1. For accurate
results allow the full
reaction period to occur.
12.
When the timer
expires, place the
Monochloramine cell
into the instrument so
that the cell tab is in the
two-o’clock position.
Make sure the sample
cell tab is completely
seated in the cell holder
slot.
Tightly cover the sample
cell with the instrument
cap.
13.
Press:
READ
The cursor will move
to the right, then
the result in mg/L
Monochloramine (as Cl
2
or chosen units) will be
displayed.
Leave the cell in the
instrument.
14.
Enter the stored
program number for
Free Ammonia.
Press:
PRGM
The display will show
PRGM?
15.
Press:
46 ENTER
The display will show
NH
3
–N
and the zero icon.
Note: For alternate forms,
press the
CONC
key.
16.
With the
Monochloramine sample
still in the cell holder,
press
ZERO
.
The cursor will move to
the right, then the
display will show:
0.00 mg/L NH
3
–N.
Remove the cell from
the instrument.
10
mL
5
mL
FA Tab
Slot
M
Tab
Slot
Nitrogen, Free Ammonia and Chloramine (Mono), continued