Quote Originally Posted by barma16 View Post
...So my silly question of the afternoon is, just what does "clear" mean in this context? When the solution first clears completely, when it stays clear after mixing, or when (if) it stays clear a minute or so after mixing? I never was much good at chemistry...
I heard that letting the sample sit after adding the 5 drops of R-0003 reagent to test for combined chlorine it will revert back to pink. When I test for FC with the R-0871 my sample turns completely clear (after so many drops)--even the undissolved crystals of the R-0870 DPD powder. My tests are right on the mark when I test before and after I add a known quantity of bleach according to the Pool Calculator.

May I ask why you wait a minute after each drop of the R-9871 reagent? I add a drop, swirl a second or two and add my next drop and so on. Sometimes I'll add up to 6 drops in rapid succession because I know that I have at least 3ppm in the pool and then swirl. Maybe I'm doing it wrong.