LaMotte 1200 Colorimeter - Manual (Page 36)

DPD CHLORINE TEST METHOD 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 mg/L Chlorine (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).
HANDLING & PRESERVATION
Chlorine in aqueous solutions, particularly weak solutions, is not stable. Exposure to
sunlight or agitation will accelerate the reduction of chlorine. Fill sample containers to
the top and cap tightly. Analyze samples as soon as possible after collection.
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 present, so that the amount of interference can be measured.
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 4.0 mg/L chlorine. To
prepare these standards, a LaMotte 250 ppm standard chlorine equivalent solution
(Code 6973) is available. Consult with your local regulatory agency to determine
standardization frequency.
LaMOTTE COMPANY
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PO Box 329 • Chestertown • Maryland • 21620 • USA
800-344-3100 • 410-778-3100 (Outside U.S.A.) • Fax 410-778-6394
Visit us on the web at www.lamotte.com
3670-01-LI · 08/08