Hach DR/700 Procedures Manual page 585

FORMALDEHYDE,
17 minutes
7.
Set a timer for a
17-minute reaction
period and proceed
immediately to Step 8.
20 seconds
10.
Shake the
cylinder vigorously
for 20 seconds.
continued
20 seconds
8.
Immediately
shake the cylinder
vigorously for 20
seconds.
Note: Important- begin
this step immediately
after setting the timer.
11.
After 5 minutes
has elapsed (12
minutes remaining)
add 2.5 mL of
Developing Solution
For Low Range
Formaldehyde to the
blank. Stopper and
invert to mix.
61-29
9.
Wait 2 minutes
(15 minutes
remaining). Then
add the contents of
one MBTH Powder
Pillow to the prepared
sample. Stopper the
cylinder.
12.
After 7 minutes
has elapsed (10
minutes remaining)
add 2.5 mL of
Developing Solution
For Low Range
Formaldehyde to the
prepared sample.
Stopper and invert to
mix.