eutech-instruments waterproof c401 colorimeter Manuel D’Utilisation
Measurement: Chlorine, Free & Total
C401/301/201/102/101
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2.4.3 Interferences
Acidity:
Greater than 250ppm CaCO3 may cause interference. To remove this
interference, neutralise a separate sample to pH6-7 using 1N Sodium
Hydroxide. Record the volume used and add the same volume of 1N
Sodium Hydroxide to the sample before carrying out the above test
procedure. Use a multiplication factor to correct for the dilution of the
sample.
interference, neutralise a separate sample to pH6-7 using 1N Sodium
Hydroxide. Record the volume used and add the same volume of 1N
Sodium Hydroxide to the sample before carrying out the above test
procedure. Use a multiplication factor to correct for the dilution of the
sample.
Alkalinity:
Greater than 250ppm CaCO3 may cause interference. To remove this
interference, neutralise a separate sample to pH6-7 using 1N Sulphuric
Acid. Note the volumes used and add the same volume of 1N Sulphuric
Acid to the sample before carrying out the above test procedure. Use a
multiplication factor to correct for the dilution of the sample.
interference, neutralise a separate sample to pH6-7 using 1N Sulphuric
Acid. Note the volumes used and add the same volume of 1N Sulphuric
Acid to the sample before carrying out the above test procedure. Use a
multiplication factor to correct for the dilution of the sample.
Hardness:
No effect at less than 2000ppm CaCO3.
Monochloramine:
Monochloramine will cause a gradual increase in the Free Chlorine result
over time. Take the test result within 1 minute of adding the reagent
sachet to avoid these errors.
over time. Take the test result within 1 minute of adding the reagent
sachet to avoid these errors.
Oxidants, including Bromine, Chlorine Dioxide, Iodine and Ozone:
These will interfere with the test method at all levels. It is recommended
that an alternative test method is used if these species are present.
that an alternative test method is used if these species are present.
Oxidised Manganese or Oxidised Chromium:
All levels will cause interference. To remove this interference:
1.
Test a 10ml sample as described in the above procedure.
2.
Adjust the pH of a separate 10ml sample to pH6-7 using 1N Sodium
Hydroxide or 1N Sulphuric Acid.
Hydroxide or 1N Sulphuric Acid.
3.
Add 1 drop of 20% Potassium Iodide Solution; swirl to mix and then
wait 60 seconds.
wait 60 seconds.
4.
Add 3 drop of 5g/l Sodium Arsenite Solution and swirl to mix.
5.
Use this as the sample in the above test procedure and make a note
of the result. Use a multiplication factor to correct for the dilution of
the sample.
of the result. Use a multiplication factor to correct for the dilution of
the sample.