When performing the FAS-DPD test, for the FC test I added drops of R-0871 until I thought the water turned clear. I then added five drops of R-0003 to perform the CC test. The solution turned pink, but then clear again upon adding 1 drop of R-0871, giving a CC of 0.5.
Since I haven't had any CCs in a while, I repeated the test. This time I added one extra drop of the R-0871 (one drop past clear) during the FC test. This time, when I added the 5 drops of R-0003 the water did not turn pink, giving a CC of 0.
I am thinking that during the first test, the solution never got completely clear during the FC test, and that's why it turned pink when adding the R-0003. Is it OK to add an extra drop of R-0871 during the FC test before performing the CC test?