- May 31, 2011
- 246
- Pool Size
- 23000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
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Salt (SWG) Pool
In a salt water pool you produce chlorine through the following reactions:
At the anode (positive plate):
2Cl- --> Cl2(g) + 2e-
At the cathode (negative plate):
2H2O + 2e- --> H2(g) + 2OH-
which nets out to the following where the chlorine gas dissolves in water:
2H2O + 2Cl- --> Cl2(g) + H2(g) + 2OH-
Cl2(g) + H2O--> HOCl + H+ + Cl-
H+ + OH- --> H2O
----------------------------------------------
2H2O + Cl- --> HOCl + OH- + H2(g)
or equivalently
H2O + Cl- --> OCl- + H2(g)
Note that the products of HOCl and OH- are exactly the same as you get when you add liquid chlorine or bleach (ignoring sodium ion). This process is partly basic, but not strongly so due to the HOCl weak acid. So the overall net result in a salt pool is simply the production of oxygen or nitrogen gasses. The disinfecting chlorine that was created from chloride ion gets converted back to chloride ion as it is "used up".
[EDIT]
The net reactions in an SWG pool for chlorine addition from the SWG and then breakdown from sunlight and oxidation of ammonia are as follows:
2H2O --> O2(g) + 2H2(g)
2NH3 --> N2(g) + 3H2(g)
The chlorine is not "seen" in the above net reactions because the chloride that became chlorine goes back to being chloride again. The oxygen gas comes from water when chlorine gas dissolved in it (i.e. from hypochlorite ion or hypochlorous acid) while the nitrogen gas comes from the ammonia (the oxygen or hydroxyl in the chlorine reverts back into water in this case, using the hydrogen from the ammonia to do so).
[END-EDIT]
Richard
I was wondering what happens to the Na+ ions in the salt water in a SWG pool.
Thanks!