Hach DR/700 Procedures Manual page 280

NITRATE, HR,
5 minutes
7.
Wait 5 minutes.
Note: A deposit of
unoxidized metal will
remain after the
NitraVer 5 Nitrate
Reagent Powder
dissolves. The deposit
will not affect test
results.
Note: An amber color
will develop if nitrate
nitrogen is present.
continued
8.
Place the blank in
the cell holder.
Note: In bright sunlight
it may be necessary to
close the cell
compartment cover.
50-30
9.
Press:
ZERO
The display will
count down to 0.
Then the display will
show 0.0 mg/L and
the zero prompt will
turn off.