R-0870 powder is used in the FAS-DPD chlorine test. The DPD chlorine test is very different.
If when you add the R-0870 the sample remains clear, your chlorine level is probably zero. However, if it goes pink for a moment and then back to clear (or brown) you haven't used enough R-0870 powder. Because of that "for a moment" thing it is good to double check with the OTO test, which is extremely reliable for chlorine vs no chlorine testing. If the sample remains clear with the OTO test, there really isn't any chlorine. Really high FC levels are the most likely to go pink for a moment and then back to clear. If OTO shows chlorine, just add more R-0870 powder.
