Thiosulfate drops for high FC pH testing?

[SunnyOptimism]

Has anyone ever used the thiosulfate drops (Taylor reagent R0007 in the TA test) to neutralize FC for doing pH testing while SLAM'ing?

Sodium thiosulfate neutralizes FC and some other test kits use it as part of their pH test procedure. The Taylor kit only uses it for the TA test.

Anyone know the how much one drop of the thiosulfate reagent reduces the FC value? Is it feasible to use that to test pH during a SLAM?


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[jblizzle]

Doesn't work. There is a thread with pictures proving this.

 

[JasonLion]

The thiosulfate does neutralize the chlorine, but it also changes the PH, which invalidates the test results. The PH reagent already contains a chlorine neutralizer and a buffer system to attempt to deal with this issue, but there is only so much chlorine you can neutralize before the results get messed up. Thus the 10/15 FC limits on the PH test. The Taylor PH test works up to an FC of 10, and is usable but reads high between FC 10 and 15. At higher FC levels it is useless.

 

[Richard320]

This is the thread mentioned: http://www.troublefreepool.com/threads/58834-Accurate-pH-test-during-shock-levels-with-R-007

The captions didn't make the transition to the new server and format for some reason. But, they're all the same water sample. First is the plain sample. Second is with high FC. Third is with thiosulfate added.

 

[SunnyOptimism]

Awesome replies once again. Thanks!!!!


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[chem geek]

If you really want to measure the pH at high FC levels, then dilute the water using distilled or deionized water (both of which are inherently is neutral in pH and contain no pH buffers). Because of the pH buffers in your test sample (mostly bicarbonate which is most of TA) the pH does not change measurably doing such dilution. You cannot use tap water or any other buffered water for this dilution.

 

[SunnyOptimism]

If you really want to measure the pH at high FC levels, then dilute the water using distilled or deionized water (both of which are inherently is neutral in pH and contain no pH buffers). Because of the pH buffers in your test sample (mostly bicarbonate which is most of TA) the pH does not change measurably doing such dilution. You cannot use tap water or any other buffered water for this dilution.

I can buy those in target cheap enough but I'm assuming purified drinking water doesn't work because of the minerals they add back in after distillation to make the water "taste right", correct?


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[JasonLion]

This only works with distilled or deionized water. Nothing else works.