Ultra Clorox Germicidal Bleach - Lower Hydroxide Level

[SBax]

I saw this product in Home Depot but I forget the price. They claim lower sodium hydroxide level than regular bleach which results in a lower pH. This could be a benefit if rising pH is a problem with heavy bleach adds in the pool. Am I correct?

http://www.cloroxprofessional.com/faqs/ucg_bleach.shtml

They formulate this product with lower hydroxide to make the chlorine more active with a lower pH upon direct dilution with water. Right?

 

[chem geek]

They said the following:

The sodium hydroxide (lye) added to bleach is for stability. Bleaches contain sodium hydroxide. Clorox® bleach has less sodium hydroxide, as reflected by its lower pH, than some private label bleaches.

This is a true statement, but applies to all of the Clorox bleaches, not just the Germicidal bleach. That is, Clorox Regular (unscented) also has a lower amount of "excess lye" in it resulting in a pH of around 11.4 which makes the net pH rise from using it (after accounting for chlorine usage/consumption which is acidic) being negligible. Off-brand Ultra bleaches often have much more excess lye with a pH of around 12.5 resulting in a noticeable pH rise over 2-4 weeks. So yes, to reduce the amount of pH rise, one can use Clorox bleach rather than an off-brand. However, at 2 ppm FC per day, the pH rise from off-brand bleach is around 0.1 every 2 weeks so not horrible.

The reason for the "excess lye" is to have the chlorine be more stable in concentrated form (i.e. when in the bottle). It has nothing to do with what happens when it is added to a pool (i.e. diluted). Most of the high pH from concentrated chlorine is just being sodium hypochlorite itself. The pH of this with no excess lye at all would be around 10.3 so the 11.4 is from the excess lye.

Richard

 

[SBax]

Wonderful! Thank you so much. Your detailed explaination is greatly appreciated.

 

[simpleton]

WOW!!! this is a great thread. very informative. thanks

 

[chem geek]

The 12.5% chlorinating liquid I get from my local pool store has a pH of around 12.5. So "per FC" it has around half of the "excess lye" as found in the off-brand Ultra bleach so at 2 ppm FC per day usage it would result in around 0.1 unit pH increase per month (at typical TA levels). In my own pool, my chlorine usage is around 1 ppm FC per month (I have a pool cover) so should theoretically have a 0.1 unit pH increase every 2 months. However, because the pool is used every day and the TA is higher (around 120 ppm or so), the pH rises somewhat more than that (from carbon dioxide outgassing) but it's not enough for me to bother with lowering the TA. I just add some acid every month or two.

 

[Woodberg]

The 12.5% chlorinating liquid I get from my local pool store has a pH of around 12.5. So "per FC" it has around half of the "excess lye" as found in the off-brand Ultra bleach so at 2 ppm FC per day usage it would result in around 0.1 unit pH increase per month (at typical TA levels).

The MSDS (see link below) for Clorox Regular Bleach says that it has a PH of 11.4. Would this mean that it would have less rise than the 12.5% chlorinating liquid you are using or does the strengh percentage difference make the Clorox raise the PH more?


http://www.thecloroxcompany.com/products/msds/bleach/cloroxregularbleach0505_.pdf

 

[dmanb2b]

only if you added the same volume of each. Even though the 12.5% may have a higher PH, you add about 50% less of it to obtain the same chlorinating effect.

 

[chem geek]

The MSDS (see link below) for Clorox Regular Bleach says that it has a PH of 11.4. Would this mean that it would have less rise than the 12.5% chlorinating liquid you are using or does the strengh percentage difference make the Clorox raise the PH more?


http://www.thecloroxcompany.com/products/msds/bleach/cloroxregularbleach0505_.pdf

The pH rise from Clorox Regular Bleach is negligible (i.e. you won't be able to detect it). It is far, far less than the chlorinating liquid with a pH of 12.5, in spite of the chlorinating liquid being twice as strong (so you use half as much for the same FC rise). Remember that pH is a logarithmic scale so the difference between a pH of 11.4 and 12.5 is over a factor of 10 in hydrogen (and hydroxyl) concentration which means that the amount of excess lye in the 12.5% chlorinating liquid at around 0.25% is around 10 times higher than that in Clorox Regular Bleach at less than 0.03%. Yes, the Clorox Regular Bleach MSDS just says the lye is < 1%, but it's a LOT less and the pH is the way to tell.

Richard

 

[Woodberg]

I saw this product in Home Depot but I forget the price. They claim lower sodium hydroxide level than regular bleach which results in a lower pH. This could be a benefit if rising pH is a problem with heavy bleach adds in the pool. Am I correct?

Just thought I would comment on the quote above that the MSDS sheets for Regular Clorox and Ultra Clorox Germicidal Bleach show that each have identical levels of sodium hydroxide and the PH level is the same. I think the above quote was refering to other generic brands of bleach. From my research, I think there is no benefit to using the commercial verison of Clorox versus regular Clorox. Right now, I'm buying 3 of the large jugs of regular Clorox at Sam's club for $7.19. I haven't found much generic bleach for much less than that.