Chemicals-1st time buyer questions

[chem geek]

Chlorine--Regular or Ultra unscented, non-sudsing, non-gelling bleach--Chlorox now has an added whitener that MAY or may NOT be good for pool water--so stay with the house brands.

Carl,

I wrote to Clorox about this and here is their response:

In April 2005 we added sodium polyacrylate. This is a polymer that binds to the minerals in the wash water. This helps prevent the minerals from reacting with the bleach and yellowing the clothes. This additive should have no effect in the use of the product in swimming pools.

This link shows a cool video about the absorbency of sodium polyacrylate which is used in many disposable diapers. In pool water, this polymer will not absorb water in the way shown because ions in the water (such as salt, bicarbonate, etc.) interact with water more readily than the polymer.

It appears that the polymer is a scale inhibitor (see this link) by inhibiting the rate of formation of calcium carbonate particles. This may mean that it adheres to pool plaster surfaces.

I wrote to Clorox with my concern that this additive could sequester calcium and that it could build up over time in pools. I'll let y'all know what I find out when I hear back from them.

Richard

[CarlD]

Richard,

Cool! So...we STILL don't know if it's a problem, a bonus or irrelevant. Still, since Chlorox costs more that generic, I'd stick with generic until we know.

CarlD

[waterbear]

It is the main ingredient in some polymeric pool water clarifiers.

[mbar]

Richard, do you think that since it sequesters calcium (which is a metal), it would help with staining in fiberglass pools? I know you will be able to explain it to me why it would work, and why not. Thanks

[chem geek]

Right now it is unclear whether this actually sequesters (binds to and reduces the effective concentration of) calcium which is what Clorox was implying or whether it just inhibits the growth of calcium carbonate crystals just slowing down the rate of scale growth but not changing its potential to form which is what was said in the link I found. This is what I asked Clorox so let's wait until I hear back from them before deciding on the effects of this chemical.

I suspect that in any event the quantity is so small (even accumulated over seasons) that it has minimal effect on the relatively large Calcium Hardness (CH) levels in pools. Based on waterbear's comment, this chemical may clarify the water and get filtered out (he also talks about this compound in this post). So I think there is a good chance that this sodium polyacrylate doesn't sequester calcium, but we'll see (Wikipedia here says that acrylates bind to metals, but take this with a grain of salt, so to speak).

Richard

[chem geek]

I just received the following response from Clorox:

Sodium polyacrylate was added to the product to bind with impurities in the water such as iron and manganese. Unfortunately, I have no information available on how it reacts with calcium. I apologize for any inconvenience this may cause.

Clorox Germicidal Bleach does not contain the Sodium polyacrylate. Unfortunately, this product is not usually available through most retail outlets. Occasionally, it may be available through club stores or home improvement stores.

So unfortunately we still don't know what this does with calcium. This link seems to indicate that calcium does get bound to sodium polyacrylate causing it to collapse (form balls) but that excess sodium reverses this. So in a pool with a higher level of (sodium) salt, there would be less sequestering of the calcium. The problem is I have no idea of the quantities we are talking about here.

As Carl says, it's safer to use an off-brand Ultra bleach that is less likely to have this additive, or the Clorox Germicidal Bleach that Clorox mentioned. I'll still try and find out more.

Richard

[mbar]

Thanks Richard, it's so nice to have someone explain it all