1—47
Chlorine, Free and Total, HR, continued
Interferences
Interfering Substance Interference Levels and Treatments
Monochloramine For conventional free chlorine disinfection (beyond
the breakpoint), monochloramine concentrations are
very low. If monochloramine is present in the
sample, its interference in the free chlorine test
varies with the temperature, the relative amount of
monochloramine to free ammonia, and the time
required to do the analysis. Approximate
interference levels of monochloramine in the free
chlorine test are listed below (as mg/L Cl
2
).
NH
2
Cl Sample Temperature °C (°F)
(as Cl
2
) 5 (40) 10 (50) 20 (68) 30 (83)
1.2 0.2 0.2 0.3 0.3
2.5 0.4 0.5 0.6 0.6
3.5 0.5 0.6 0.7 0.8
5957088.book Page 47 Friday, March 22, 2013 3:54 PM
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