Trouble getting CC to zero.

[chem geek]

Dave,

The FAS-DPD chlorine test can measure Free Chlorine and Combined Chlorine each to 0.2 ppm since using a 25 ml sample size has one drop of titrant measure 0.2 ppm (the 10 ml sample size has one drop measure 0.5 ppm). You add 2 dippers of R-0870 powder which makes the sample turn pink if free chlorine is present, then add R-0871 dropwise until the sample turns colorless. The count of drops is Free Chlorine. Now you add 5 drops of R-0003 and the sample will turn pink if combined chlorine is present, then add R-0871 dropwise until the sample turns colorless. The count of drops (after adding the R-0003) is Combined Chlorine.

Richard