What does it mean when you say the sun "burns off" chlorine?

[doncaruana]

Does that mean that it breaks it down so that it re-bonds in the pool? I can't imagine it just turns into chlorine gas and escapes...does it? Otherwise, the principal of an SWG wouldn't seem to work (you'd have an ever-falling level of chlorine with nothing for the sodium to bond to).

So can someone explain that to me? I don't need to know for any maintenance purposes...I'm just a dyed-in-the-wool geek.

 

[gboulton]

Re: What does it mean when you say the sun "burns off" chlor

From waaaaaaaaaaaaay back in the dusty corner of my brain, during a conversation about de-chlorinating tap water for fish tanks, I seem to remember...

2OCl- --> O2 + 2Cl-

Our bleach produces Hypochlorite ions, which do the work of destroying organics. However, they're relatively unstable, and bombardment by UV light splits them into O2 (Oxygen molecules) and a Chlorine ion...which then, yes, outgasses.

I'm betting chem geek can come along and provide a more thorough and descriptive answer, but that's what my dusty old memory tells me anyway.

 

[JasonLion]

Re: What does it mean when you say the sun "burns off" chlor

The detailed chemistry is explained in this post. The oxygen gas escapes, but the chloride ion stays in the water, essentially it becomes salt.

 

[doncaruana]

Re: What does it mean when you say the sun "burns off" chlor

Thanks! So MUCH info here! The "dad" and "pool owner" in me are fighting with the "engineer" and "geek" in me for which to consume first!!

I'm an IT guy by trade, an electrical engineer by degree and a geek in every other way. I set the class curve in chem in college (means nothing now, of course), but I *loved* chemistry back then! It was like math with consequences!

 

[gboulton]

Re: What does it mean when you say the sun "burns off" chlor

Thanks for that link, Jason. Good stuff! I see my memory was "ok" but significantly oversimplified, and wrong about outgassing. Thanks for offering education.

 

[chem geek]

Re: What does it mean when you say the sun "burns off" chlor

Even the post I wrote that Jason linked to is an oversimplification, but shows the net result. In reality, the UV in sunlight breaks apart chlorine into radicals which eventually produce chloride ion and oxygen gas (technical details in this new post).