Chem_Geek: Heeeeeeelllllllpppppppp!!!

[LexPlayer]

Thiosulfate is supposed to reduce chlorine directly and not form combined chlorines. There are many possible reactions, but one of them is the following:

Na2S2O3•5H2O --> 2Na+ + S2O3(2-) + 5H2O

2S2O3(2-) + HOCl --> S4O6(2-) + OH- + Cl-

There are other reactions that take the thiosulfate all the way to sulfate or even sulfur, but I believe these are less likely. None of them form combined chlorine -- all produce chloride ion. The oxidation potentials are as follows:

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Richard

Between your post and the chemical anlayis on this page, my eyes have gone buggy!

If Professional Pool Operators of America (PPOA) is correct, I would think that Sodium Sulfite is a better option than Sodium Thiosulfate beause there is no free Sulfur floating around "sulfinating" the water up.

I assume the Sodium sulfate (or Glauber's salt, sodium sulfate decahydrate, Na2SO4·10H2O per wikipedai) is just diluted into the water.

Anyway, I still don't know what my chlorine level is, but I'm trying to find a DPD test kit locally.

[waterbear]

Do yourself a favor and forget the DPD kit and get an FAS-DPD kit. It's easier, more accurate, and can test much higher chlorine levels with an accuracy as great as .2 ppm!

[CarlD]

Evan's right--you are just wasting money--and you'll have to get a FAS-DPD test kit sooner or later anyway.

DPD only goes to 15ppm before it bleaches out--looking like you have NO chlorine!