Hach DR/700 Procedures Manual page 635

OZONE,
continued
11.
Place the
AccuVac ampul
containing the blank
into the cell holder.
Note: In bright sunlight,
it may be necessary to
close the cell
compartment cover.
SAMPLING
The chief consideration when collecting a sample is to prevent the
escape of ozone from the sample. The sample should be collected
gently and analyzed immediately. Warming the sample, or disturbing
the sample by stirring or shaking, will result in ozone loss. After
collecting the sample, do not transfer it from one container to another
unless absolutely necessary.
STABILITY OF INDIGO REAGENT
Indigo is light-sensitive. Therefore, the AccuVac ampuls should be kept
in the dark at all times. However, the indigo solution decomposes
slowly under room light after filling with sample. The blank ampul can
be used for multiple measurements during the same day.
SUMMARY OF METHOD
The reagent formulation adjusts the sample pH to 2.5 after the ampul has
filled. The indigo reagent reacts immediately and quantitatively with ozone.
The blue color of indigo is bleached in proportion to the amount of
ozone present in the sample. Other reagents in the formulation prevent
12.
Press:
READ
The display will
count down to 0.
Then the display will
show the result in mg/
L ozone (O ).
3
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