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pH
Ionic strength, temperature and other water factors will have an effect on
pH readings. This test has been calibrated for conditions most likely to be
encountered in a typical swimming pool.
The colour range of the phenol red test is yellow, through orange, to red.
The formation of an intense purple coloration shows that the indicator has
been affected by high chlorine or bromine residuals. In such cases the
result should be disregarded.
Alkalinity
The Alkaphot test contains an organic acid titrant to neutralise the total
alkalinity in the sample. This acid is finely sieved during manufacturing to aid
solubility, but the tablet requires thorough crushing and mixing to ensure full
dissolution of the active ingredient. The test should be allowed to stand for one
minute after mixing. If a thin yellow layer is observed at the bottom of the
tube, the test should be thoroughly remixed before measurement.
Ozone
Ozone, free and combined chlorine and bromine residuals all react with DPD
4 reagent to produce a pink colour, proportional to the concentration
present in the sample.
Glycine destroys ozone in the sample and the colour produced in the DPD
test then corresponds to the chlorine and bromine only.
The ozone content is thus obtained by the difference between the test
readings with and without glycine.
Cyanuric Acid
Allow the tablet to disintegrate slowly, for at least two minutes, before
crushing any remaining tablet. This encourages the development of an
even, fine turbidity and enhances reproducibility of results.
The range of the cyanuric acid (CNA) test is 2 - 200 mg/l. Higher levels can
be tested by first diluting the sample with mains or deionised water and
then applying the appropriate dilution factor. Palintest’s Dilution Tube
(PT 512), which is available as an optional extra, should be used for the
dilution.
Summary of Contents for Pooltest 25
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