Pool Water Chemistry (Warning: Can Get Technical)

[chem geek]

I wasn't sure where to put this interesting piece of info, so I'm putting it here in the Pool Water Chemistry thread since it is related to the chlorine/CYA relationship. This link describes a patent where a fluid is initially viscous in order to carry particulate matter and then becomes less viscous (more fluid) over time in order to deposit or settle its particulate matter. The patent uses a thickener, a hypochlorite, and cyanuric acid. Differing ratios of the CYA to chlorine determine how quickly the thickener breaks down (which changes the viscosity of the water). It's interesting that this is a patent that DEPENDS on the chlorine/CYA relationship for its proper functioning in having only disinfecting chlorine (that is, chlorine not bound to CYA and probably only hypochlorous acid) break down the thickener and having that concentration (and therefore reaction rates) be dependent on the chlorine/CYA ratio.

Richard

[chem geek]

I didnt think this post deserved its own thread, but it is some useful info regarding ozone and chlorine. waterbear (Evan) and I worked out how ozone could oxidize chlorine since there were some reports of people using ozonators finding greater chlorine usage (loss). The following is apparently what happens:

O3 + H2O + 2e --> O2 + 2OH- ............ Eo = +1.24V
OCl- + 2OH- ... --> ClO2- + H2O + 2e .. Eo = -0.66V
-------------------------------------------------------------
O3 + OCl- ...... --> O2(g) + ClO2- ........ Eo = +0.58V
Ozone + Hypochlorite ion --> Oxygen + Chlorite ion

O3 + H2O + 2e --> O2 + 2OH- ............ Eo = +1.24V
ClO2- + 2OH- .. --> ClO3- + H2O + 2e .. Eo = -0.33V
-------------------------------------------------------------
O3 + ClO2- .... --> O2(g) + ClO3- ......... Eo = +0.91V
Ozone + Chlorite ion --> Oxygen + Chlorate ion

With the net result being the following:

2O3 + OCl- ... --> 2O2(g) + ClO3- ......... Eo = +1.49V
Ozone + Hypochlorite ion --> Oxygen + Chlorate ion

So ozone will oxidize chlorine to form chlorate. This is a very strong (likely) reaction, but the above info does not determine the rate of the reaction.

Richard