Cyanuric acid and bleach

[JamesW]

Split off of this topic. JasonLion

Do not pour bleach directly on the cyanuric acid. Dilute the bleach and add it away from the cyanuric acid.

The reaction of an isocyanurate with hypochlorite can result in rapid formation of nitrogen trichloride, which at high enough concentrations will detonate spontaneously with great violence.
http://www.taylortechnologies.com/Chemi ... ntentID=73

 

[JasonLion]

Re: Can I pour liquid bleach over my CYA ?

Cyanuric acid, used to raise the CYA level, is not an isocyanurate, and thus not explosive when mixed with bleach. Dichlor and trichlor are both isocyanurates, and can explode when mixed with bleach.

 

[chem geek]

Re: Can I pour liquid bleach over my CYA ?

I think you meant to say that CYA is not a chlorinated isocyanurate, but your point is still valid. Anyway, there's not much point pouring bleach literally on top of the CYA anyway -- it can just be poured over another return flow or if there is only one return then further away from the return.

 

[JamesW]

Re: Can I pour liquid bleach over my CYA ?

Adding the bleach near the cyanuric acid with a good flow of water should probably not cause any problems. However, I believe that it is a best practice to avoid adding chemicals in close proximity to each other.

Cyanuric acid can be oxidized by hypochlorite, in concentrated solutions, in the following manner, forming nitrogen trichloride as an intermediate.

H₃Cy + OH^- --> H₂Cy^- + H₂O

Cyanuric acid + hydroxide --> Cyanurate + water

H₂Cy^- + 2ClO^- --> Cl₂Cy^- + 2OH^-

Cyanurate + hypochlorite --> dichloroisocyanurate + hydroxide

Cl₂Cy^- +7ClO^- + 4H₂O --> 3NCl₃ + 2CO₂ + HCO₃ ^- + 7OH^-

Dichloroisocyanurate + hypochlorite + water --> Nitrogen trichloride + carbon dioxide + bicarbonate + hydroxide

3NCl₃ + 9OH^- --> 1.5N₂ + 4.5ClO^- + 4.5Cl^- + 4.5H₂O

Nitrogen trichloride + hydroxide --> nitrogen gas + hypochlorite + chloride + water

Overall:

H₃Cy + 4.5ClO^- --> 1.5N₂ + 4.5Cl^- + 3CO₂ + 1.5H₂O


Reference

 

[JasonLion]

This side conversation has been moved to The Deep End. Please do not post advanced chemistry in the Just Getting Started area. Thanks JasonLion

 

[chem geek]

This post I wrote a while ago talks about the oxidation of CYA by chlorine, but this isn't a particularly fast process. At any rate, it is a good idea to avoid mixing concentrated chemicals in general. Particularly troublesome is Cal-Hypo and Trichlor as shown in this link while this link shows that Cal-Hypo's flammability is a function of its concentration. Also troublesome is acid with chlorine.