Conflicting test results...........

[CarlD]

Frankly, the only OTO/pHenol kit I trust is Taylor one, but the K-2006 FAS-DPD test for Free Chlorine and Combined Chloramines is the gold standard. It is simply the most accurate and reliable test a home-owner can buy.

[pmaru77]

If the K-2006 is the gold standard, then why do they not specify that the scoop of powder should be flat)level) or heaping? Or does it not matter?

[SunnyOptimism]

It does not matter. The powder is simply the indicator dye that you are saturating the solution with to bind to the FC and cause the pink color change. The titrating reagent is the exact solution that then neutralizes the FC and turns the solution from pink to clear. So the only thing that matters is having a known titrating reagent concentration to set the ppm/drops value.

If you look at the scoop handle, it is printed with 0.05gm. So two level scoops adds approximately 0.1gm of DPD powder which is more than enough to react with all of the FC in your test sample.

[FormerBromineUser]

We usually say that if 1/2 scoop turns the water pink, then that's enough.

[JimK]

We usually say that if 1/2 scoop turns the water pink, then that's enough.

Some time ago I read that one scoop was sufficient if it turned the sample pink. Out of curiosity I compared using one scoop vs two (as recommended in the Taylor instructions); both turned the sample pink and both resulted in the same FC measurement.

[CarlD]

Yup. That's what we have been telling you all for years.

[chem geek]

We usually say that if 1/2 scoop turns the water pink, then that's enough.

The main reason to use one level scoop for a 10 ml sample and a heaping scoop or possibly two level scoops for a 25 ml sample is to have a stronger color transition at the end of the titration. With too few scoops, you may undercount but probably by only one drop which is usually not a big deal.