Sciencemadness Discussion Board

Pool sanitizing (cyanurates and hypohalites) ?

stygian - 5-7-2005 at 11:42

I got a few questions about the chemistry behind pool chlorination/bromination.

The traditional sanitizing agent has been hypochlorous acid in some form (calcium, sodium, or Cl2 + H2O). It has excellent oxidizing and sanitizing properties but is unstable. Cyanuric acid/cyanurates are in use nowdays to overcome this. How does HOCl react with cyanuric acid? Does it convert it to the commonly used isocyanuric chlorides ("stabilized chlorine";)? If so, how do these compounds oxidize/sanitize the water? Do they revert to hypochlorous acid somehow or do they react in their own way to do their job?

Also, I read that bromide can be oxidized to hypobromite with e.g. persulfate, but chlorides cannot. Is this true?

[Edited on 5-7-2005 by stygian]

Chris The Great - 5-7-2005 at 16:29

Cyanuric chloride reverts to cyanuric acid and hypochlorous acid in water. I'm not sure if you can turn it back when water is present however, they may just stay seperate or in an equilibrium.
Industrially cyanuric chloride is made by cyranuric acid + sodium hydroxide + chlorine gas.

I think with the cyanuric acid stabilizis the HClO after it has been released by hydrolisis.