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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.
Cyanuric Acid
:
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.
Calcium Hardness
:
The expression of hardness results sometimes causes
confusion. It is normal practice to express the results
of hardness tests as mg/l CaCO
3
(calcium carbonate).
This is merely a convention to allow the comparison of
different results and does not necessarily indicate that
the hardness is present in the water in this form.
Results may also be expressed in literature as mg/l Ca.
The instrument will not do this calculation automatically
but to convert mg/l CaCO
3
to mg/l Ca multiply by 0.4.
29
Bromine
:
For most purposes it is sufficient to simply measure the
total bromine residual (using DPD No 1 tablets) since
both free and combined bromine are active disinfectants.
Note that a too high bromine level (above 20 mg/l) can
cause bleaching of the pink colouration formed in the
DPD test and give a false negative or low result. If a
colourless or weakly coloured test solution is obtained
when bromine is known to be present, check for the
possibility of bleaching by repeating the test on a sample
diluted with bromine/chlorine-free water.
Water Balance:
In swimming pools, the effects of the pH, hardness and
alkalinity are all inter-related. The likelihood of corrosive
or scale problems can be predicted using the Palintest
Water Balance Calculation. The resulting value indicates
to users the corrosion or scale forming tendency of the
water. The Palintest method is a simplified version of the
Langelier Index and this can be calculated from the
Palintest result by subtracting 11.1.
Calculation
:
1
Take a sample of the water and measure the calcium
hardness. Using the table overleaf, read off the factor
which corresponds nearest to the calcium hardness value
measured. Record this Calcium Hardness Factor (Line 1).