Hach DR/700 Procedures Manual page 511

FLUORIDE,
1 minute
7.
Wait 1 minute.
10.
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.
continued
8.
Insert the
AccuVac Vial
Adapter into the cell
holder.
11.
Place the
prepared sample in
the cell holder.
Note: In bright light it
may be necessary to
close the cell
compartment cover.
57-5
9.
Place the blank in
the cell holder.
Note: In bright light, it
may be necessary to
close the cell
compartment cover.
12.
Press:
READ
The display will
count down to 0.
Then the display will
show the results in
mg/L fluoride.
Note: If the instrument
flashes the upper range
limit, dilute the sample
with an equal volume of
demineralized water
and repeat the test,
using this solution in
Step 4. Multiply the
result by 2.