14
Chlorine
Range
Cl
2
5 : 0.01 – 5 mg/l
Cl
2
10 : 0.01 – 10 mg/l
Wavelength – 530 and 575 nm
Method – DPD
Free Chlorine
1 Rinse test tube with sample leaving a few drops in
the tube.
2 Crush the DPD No 1 tablet (or DPD-XF for high
range instruments) in two or three drops of the
water sample until the tablet is thoroughly crushed.
3 Add the 10 ml test solution, mix and seal the tube
with the cap.
4 Gently invert the tube to remove any bubbles from
the inner walls of the tube.
5 Take photometer reading.
6 Retain test solution if total chlorine test required
(see overleaf for further instructions).
15
Total Chlorine
1 Carry out this test on the solution remaining from
the Free Chlorine test.
2 If any non-chlorine shock treatment chemicals have
been added to the pool, see additional notes below.
3 Add one DPD No 3 tablet (or DPD-XT for high
range instruments), crush and mix to dissolve.
4 Stand for two minutes.
5 Take photometer reading. Ensure the display
shows the test range that you desire.
To obtain COMBINED CHLORINE residual, subtract
Free Chlorine result from Total Chlorine result :-
ie Combined Chlorine = Total Chlorine - Free Chlorine
For notes on chlorine testing, see overleaf.
Notes
• If any non-chlorine shock treatment chemicals have
been added to the pool, add one DPD Oxystop (AP
017) tablet, crush and mix to dissolve prior to
adding the DPD No 3 tablet to the test solution.
Stand for one minute before proceeding. This will
prevent a response caused by the shock treatment
chemicals.
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