Numbers = confusion

[chem geek]

The Tatlor website lists no official interferences for that test but I tried the CYA test several times at 30ppm FC and got a value that was 30ppm lower than at Target FC levels.

It is possible that at high FC levels that these chlorinated isocyanurates do not precipitate with melamine in the CYA measurement test because the chlorine is where the hydrogen would be in CYA so no hydrogen bonding occurs. The CYA level could measure lower by as much as the FC level.

This is easily overcome by dechlorinating the water sample such as by using the Taylor R-0007 thiosulfate reagent or other reducing agent such as hydrogen peroxide. One would add this to the water sample before adding the melamine.

[CarlD]

Thanks for the clarification and useful "hack", Richard!