Hach DR/700 - Page 586

61-30
FORMALDEHYDE, continued
13. Just before 15
minutes has elapsed
(2 minutes
remaining), fill a
10-mL cell to the
10-mL line with the
blank. Cap.
Note: Pouring the
solution slowly into the
cell will avoid bubble
formation on the cell
walls. If bubbles form,
swirl the cell to dislodge
them.
14. After the 15
minutes has elapsed,
place the blank in the
cell holder.
Note: In bright light, it
may be necessary to
close the cell
compartment cover.
15. Press: ZERO
The display will
count down to 0.
Then the display will
show 0 µg/L and the
zero prompt will turn
off.
16. Fill a 10-mL cell
to the 10-mL line
with the prepared
sample. Cap.
17. Place the
prepared sample in
the cell holder.
Note: In bright light, it
may be necessary to
close the cell
compartment cover.
18. When the
17-minute period is
over, immediately
press:
READ
The display will
count down to 0.
Then the display will
show the results in
µg/L formaldehyde
(CH
2
O).