Total Alkalinity Test - At what point to record value

Jul 10, 2013
490
Northern Howell, NJ
When I test, I tend to test for a range. And that is typically good enough for me. But this forum recently told me to get my pH from 80 down to 60 to help control the fast rise of pH. My question is this, when I start adding the reagent to turn the color of the solution from green to red, there are degrees of the change of color and I am not sure which is the accurate reading.

This is a typical test for me:
<no speedstir>
Fill to 25ml mark
2 drops R-0007 swirl
5 drops R-0008 Swirl (solution is green)
add R-0009 dropwise while swirling - after the 6th drop, the green turns into almost a dark purple color. Then the 7th drop, it clearly has turned red. The 8th drop the red has become more vibrant. And finally the 9th drop there is no discernible change from what it look like after 8. In other words 8 and 9 look identical.

So in the past I really didn't care EXACTLY what my reading was. I knew it started changing at 60 and stopped changing after 80. If I was happy with that range, I moved on. But now I am being told that the difference between 80 and 60 can make a huge difference in pH rise. So I want to know, what is the accurate number based on my described test above? 60? 70? or 80?

FYI - When I perform a CH test, the same concept applies.
 
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