free chlorine sampling

[feaz]

When testing for free chlorine and after adding 2 dips of R-0870 then drops of R-0871 until water clears I typically let the sample set for 5-10 minutes and the water again turns light pink. I'm pretty sure the 0870 has completely dissolved but surely this has to be the reason for the sample to change back to pink. Typically clears back up after 1-2 drops but not sure if I can count this as free chlorine. Yes or no?

 

[Jezza]

No you don't count. Once you add drops of 0871 to clear that is your reading which is also why it is important to move through the FAS DPD test fairly quickly about 1 drop per second.

 

[woodyp]

No need to expect ALL the powder to dissolve.