LaMotte 1200 Colorimeter - Manual (Page 35)

er2
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 (0290). 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.
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).
11.
9. 10.
12.
Push the
button.
Record reading
as ppm Total
Residual
Chlorine.
READ
Cap and
invert to
mix.**
Insert the tube
into the
chamber, being
sure to align
the index line
with the arrow
on the meter.
Close the lid.
I200
COLORIMETER
••••••••••••••••••
READ
2.55
ZERO
Add 5 drops *DPD
#3 Total Chlorine
Reagent (6743) to
the sample from
Step 7.
13.