LaMotte 1200 Colorimeter - Manual (Page 31)

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TOTAL RESIDUAL CHLORINE
If either chlorine reading displays , repeat procedure on diluted sample, and
multiply the result by the appropriate dilution factor. See 1200 Colorimeter Instruction
Manual for procedure.
Levels of chlorine above 10 mg/L will cause a bleaching effect on the DPD indicator, and
may give a false indication that no chlorine is present. If it is possible that the chlorine
concentration is greater than 10 mg/L (e.g. after shock treatment), perform test on a
diluted sample and multiply the result by appropriate dilution factor.
CAUTION: DO NOT leave reacted DPD samples in test tubes. Discard sample and
thoroughly rinse tubes. If allowed to remain, DPD will stain tubes, significantly
impairing the operation of the 1200 Colorimeter. If necessary, acid wash, and vigorously
clean glassware with test tube brush and detergent.
**For wastewater samples, Standard Methods for the Examination of Water and Wastewater
recommends waiting 2 minutes for full color development.
11.
9. 10.
12.
••••••••••••••••••
READ
2.55
ZERO
COLORIMETER
I200
Cap and mix
until tablet
disintegrates.**
Push the
READ button.
Record reading
as ppm Total
Residual
Chlorine.
Insert the tube
into the
chamber, being
sure to align the
index line with
the arrow on
the meter.
Close the lid.
Subtract the Free Available
Chlorine reading from the
Total Residual Chlorine
reading to determine ppm
Combined Chlorine
(Monochloramine,
Dichloramine, and Nitrogen
Trichloride) present in the
water sample.