Quote Originally Posted by chem geek View Post
CYA
Taylor doesn't talk about this, but it seems that chlorine bound to CYA does not form the melamine-cyanurate precipitate which means that the CYA test will read artificially too low when the FC is high. This should be able to be handled by adding around 2 drops of R-0007 thiosulfate to the water sample for every 10 ppm FC before you add the CYA reagent.
It would be interesting to test this with FC levels of 20, 30, 40 PPM... both with and without the thiosulfate.