LaMotte DPC-52 Water Testing Laboratory - Manual (Page 9)

CYANURIC ACID
Cyanuric acid is added to swimming pool water as a stabilizing agent for free available
chlorine. It minimizes the loss of chlorine in pool water due to the action of ultraviolet
rays from sunlight. After the pool has been stabilized with cyanuric acid, the free
available chlorine residual should be maintained at the recommended level of 1.5 ppm
to ensure proper sanitation.
The recommended level of stabilizer in pools is between 25 and 100 ppm. When
readings above 150 ppm are encountered, it may be necessary to replace some of the
pool water with fresh make-up water to reduce the concentration of cyanuric acid. If
stabilizers are used, follow the manufacturer’s instructions for their product to maintain
the recommended levels of cyanuric acid.
RANGE:
10 - 200 ppm (Readings below 10 ppm may not be reliable.)
METHOD:
A buffered solution of melamine forms a precipitate with
cyanuric acid in proportion to the amount of cyanuric acid
present. The density of particles in suspension is measured
turbidimetrically.
INTERFERENCE:
No known interference from compounds normally found in
pool water. For best results, the temperature of the sample
should be between 70°F and 80°F. As the temperature of the
sample increases, cyanuric acid readings will decrease even
though the actual concentration has not changed.
PROCEDURE
1. Use the 5 mL syringe (0807) to dispense 5 mL of *Cyanuric Acid Reagent
(WL-4856) into the colorimeter tube (0967). Dilute to the 10 mL line with pool
water sample.
2. Cap tube and mix thoroughly. The development of a white precipitate indicates the
presence of Cyanuric Acid.
3. Wait one minute. With the “Cyanuric Acid” text appearing on the meter display,
mix and insert the treated sample into the colorimeter chamber. As soon as the
display stabilizes, read result in ppm Cyanuric Acid.
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