LaMotte DPC-52 Water Testing Laboratory - Manual (Page 6)

PROCEDURES
A. FREE AVAILABLE CHLORINE
1. Fill the water sample bottle (0688) with the pool water sample.
2. Dispense the water sample into a clean colorimeter tube (0967), until the tube is
filled to the 10 mL line.
3. Insert the tube containing the untreated sample into the colorimeter chamber, and
press the “Chlorine” button once. When the display indicates “Blank 0.0,” press the
“Chlorine” button again. Remove tube.
4. Add 5 drops of DPD 1A Free Chlorine Reagent (P-6740) and 5 drops of *DPD 1B
Free Chlorine Reagent (P-6741).
5. Cap and mix. The development of a pink color indicates the presence of Free
Available Chlorine.
6. Insert the treated sample into the colorimeter chamber. Read result in ppm Free
Available Chlorine. Do not discard this treated sample if the test for Total Chlorine
is to be made.
B. TOTAL RESIDUAL CHLORINE
1. Add 5 drops of *DPD #3 Total Chlorine Reagent (P-6743) to the sample from Step
A.6. Cap and mix. An increase in color indicates the presence of Combined
Chlorine.
2. Insert the treated sample into the colorimeter chamber and press the “Chlorine”
button. As soon as the display stabilizes, read result in ppm Total Residual Chlorine.
C. COMBINED CHLORINE
The Combined Chlorine concentration equals the difference between the Total
Residual Chlorine reading (B.2.) and the Free Available Chlorine reading in (A.6.)
above.
Total Residual Chlorine
- Free Available Chlorine = Combined Chlorine
A Combined Chlorine level of 0.2 ppm or greater should be treated.
NOTES:
· If either Chlorine reading exceeds 5.0 ppm, the display will flash, repeat the test
procedure on a diluted sample and multiply the test result by the appropriate dilution
factor.
· Levels of Chlorine above 10 ppm can cause a bleaching effect of the DPD indicator
and may give a false indication that no chlorine is present. If it is possible that the
chlorine concentration may be greater than 10 ppm (e.g., after shock treatment),
perform the test on a diluted sample and multiply the test result by the appropriate
dilution factor.
· If, after adding both DPD 1A Free Chlorine Reagent and *DPD 1B Free Chlorine
Reagent, a cloudy precipitate is present, retest by adding reagents first and water
sample second to the tube.
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