LaMotte SMART3 Colorimeter - Manual (Page 118)

APPLICATION: Drinking, surface, and saline waters; swimming pool water;
domestic and industrial wastes.
RANGE: 0.00–4.00 ppm Chlorine
MDL: 0.03 ppm
METHOD: In the absence of iodide, free available chlorine reacts
instantly with DPD to produce a red color. Subsequent
addition of potassium iodide evokes a rapid color response
from the combined forms of chlorine (chloramines).
SAMPLE
HANDLING &
PRESERVATION:
Chlorine in aqueous solutions is not stable, and the chlorine
content of samples or solutions, particularly weak solutions,
will rapidly decrease. Exposure to sunlight or agitation
will accelerate the reduction of chlorine present in such
solutions. For best results, start analysis immediately after
sampling. Samples to be analyzed for chlorine cannot be
preserved or stored.
INTERFERENCE: The only interfering substance likely to be encountered in
water is oxidized manganese. The extent of this interference
can be determined by treating a sample with sodium
arsenite to destroy the chlorine present so that the degree
of interference can be measured.
Iodine and bromine can give a positive interference, but
these are not normally present unless they have been
added as sanitizers.
CHLORINE, DPD Tablet SMART3 Test Procedures 11.10
Test P
rocedures