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TEST METHODS SPECIFICATIONS
„ APPLICATION
Drinking water supplies and distribution systems, swimming pool and
spas, sewage and chlorinated waste waters, process waters and sanitizing
solutions.
„ RANGE
0 to 4.0 ppm Chlorine (may be extended by dilution)
0 to 7.0 ppm Bromine (may be extended by dilution)
„ METHOD
In the absence of Iodide, Free Available Chlorine reacts instantly with the
buffered diethyl-p-phenylenediamine indicator (DPD) to produce a red color
in proportion to the amount of chlorine present. Subsequent addition of
potassium iodide produces a rapid color response from the combined forms
of chlorine (chloramines). In buffered samples, bromine reacts with disthyl-
p-phenylene diamine (DPD) to produce a pink-red color in proportion to the
concentration of bromine present.
„ HANDLING & PRESERVATION
Chlorine and bromine in aqueous solutions, particularly weak solutions, are
not stable. Exposure to sunlight or agitation will accelerate the reduction of
chlorine and bromine. For chlorine samples, fill sample containers to the top
and cap tightly. Analyze samples as soon as possible after collection. Samples
to be analyzed for bromine cannot be preserved or stored.
„ INTERFERENCES
The only interfering substance likely to be encountered is oxidized
manganese. The extent of this interference can be determined by treating
a sample with sodium arsenite to destroy the chlorine or bromine present,
so that the amount of interference can be estimated. Iodine, bromine and
chlorine can also interfere, but these are not normally present unless they
have been added as additional sanitizers.
„ CALIBRATION
The single test colorimeter is precalibrated. In order to comply with NPDWR or
NPDES reporting regulations, the calibration should be checked periodically
by using a set of reference standards including a 0 mg/L blank and 0.3, 1.0,
and 3.5 mg/L chlorine. To prepare these standards, a LaMotte 1000 mg/L
standard chlorine equivalent solution (Code 3858) is available. Consult with
your local regulatory agency to determine standardization frequency.
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