Cya/hypochlorous acid and hypochlorite interaction.

[C.Johnson]

Quote taken from the thread Chlorine after cya bond is released

With no cyanuric acid in the water, the pH does determine the percentage of hypochlorite vs. hypochlorous acid.


The pKa of hypochlorous acid is about 7.53.


1÷(1+10^(7.53 – pH)) = hypochlorite percentage.


For example:


pH..........hypochlorite percentage


8.53..........0.90909

8.00.........0.747

7.53.........0.50

7.30.........0.37


Hypochlorous acid and hypochlorite both oxidize and sanitize, but hypochlorous acid is better at both.


With cyanuric acid in the water, the equation changes because most of the chlorine is bound to cyanuric acid, but the pH does still effect the ratio. The effect is not as great, but it still matters somewhat.

If I am understanding correctly, the chlorine atom bonded to the CYA molecule is neither hypochlorous acid nor hypochlorite ion.

James gives an excellent formula and chart for the ratio of HCLO to CLO- given pH when CYA is not present.

My question is: Is there any way to know how that pH-ratio relationship changes given, say, a set amount of CYA?

Thanks!

 

[mas985]

Do you mean this:

Pool Water Chemistry

This thread presents my findings so far on pool water chemistry including the following: More Accurate Calcite Saturation Index (CSI) to replace Langelier Saturation Index (LSI) Calculation of ppm HOCl (disinfecting chlorine) at various levels of Total Free Chlorine (FC) and Cyanuric Acid (CYA)...

www.troublefreepool.com

 

[JoyfulNoise]

Do you mean this:

Pool Water Chemistry

This thread presents my findings so far on pool water chemistry including the following: More Accurate Calcite Saturation Index (CSI) to replace Langelier Saturation Index (LSI) Calculation of ppm HOCl (disinfecting chlorine) at various levels of Total Free Chlorine (FC) and Cyanuric Acid (CYA)...

www.troublefreepool.com

Unfortunateky, tgere are two graphs missing which answers the OP’s question.

The graph on the left cannot show the 0% flat line for Cl-CYA since it is off the chart (the 0% is at negative infinity since this is a logarithmic scale).

https://www.troublefreepool.com/~richardfalk/pool/HOCl-OCl-noCYA-log.gifhttps://www.troublefreepool.com/~richardfalk/pool/HOCl-OCl-30CYA-log.gif

How's that?

P.S.
It is interesting to note that the tradi

 

[JamesW]