LaMotte SMART 2 - Manual (Page 106)

Chlorine can be added in the form of chlorine gas, liquid sodium hypochlorite
(bleach), granular calcium hypochlorite or as organic chlorine compounds.
Chlorine is not present in natural water supplies; if it is present it is the result
of chlorination of a water supply or of chlorinated compounds being discharged
as waste from industrial operations. The presence of chlorine in concentrations
above 0.5 parts per million should be considered evidence of pollution from
chlorine treated effluents or from a process in which high concentrations of
chlorine are used.
APPLICATION: Drinking, surface, and saline waters; swimming pool water;
domestic and industrial wastes.
RANGE: 0.00–10.00 ppm Chlorine
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, Total–UDV 2/3 Smart2 TEST PROCEDURES 2.04