Drop count test results

[Tyrone Shuz]

When doing a DPD CL test or a TA test, do you take the first number when the color changes initially, or the last number when the color gets more intense in that direction? For example, in the CL test, do you take the number when the pink goes away, or the next drop when it's /really/ clear?

Same with TA, do you wait till it turns pink, or wait till it's even redder to mark down the number?

 

[KurtV]

Keep adding drops (and swirling) until you get no additional color change. Don't count the drop that didn't produce any additional change. In other words, if the 8th drop changes the TA test from green to reddish, the ninth drop deepens the red color, and the tenth drop doesn't change the color any more, your count is nine drops or 90 ppm. The chlorine test works the same way except that you add drops until the sample doesn't get any clearer (e.g. if the third drop leaves you with a slight pink cast, the fourth drop makes it clear, and the fifth drop produces no change, your count is four drops).

 

[Tyrone Shuz]

Keep adding drops (and swirling) until you get no additional color change. Don't count the drop that didn't produce any additional change. In other words, if the 8th drop changes the TA test from green to reddish, the ninth drop deepens the red color, and the tenth drop doesn't change the color any more, your count is nine drops or 90 ppm. The chlorine test works the same way except that you add drops until the sample doesn't get any clearer (e.g. if the third drop leaves you with a slight pink cast, the fourth drop makes it clear, and the fifth drop produces no change, your count is four drops).

Thank you very much. I /thought/ this may have been the case, but it never hurts to make sure.