Total Alkalinity only goes to yellow

[rick458]

Using Leslies kit goes to green, but titrates only to yellow (50 drops)
does that mean TA is really low or very high and I did not hit final titration point?

FC was 10+ could it be just bleaching the result?

 

[chem geek]

Yes, at high FC the TA test goes from blue to yellow instead of from green to red. You can add more sodium thiosulfate drops (R-0007) to the initial water sample to neutralize the chlorine. If you can see the transition in color, the test is still valid.

The TA indicator dye is a mixture of bromocresol green that goes from blue to yellow and methyl red that goes from yellow to red. So when both dyes are active you go from blue+yellow=green to yellow+red=red. High FC levels react with the methyl red dye leaving only the bromocresol green dye that goes from blue to yellow.