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Thread: Sodium dithionite - iron out

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    Sodium dithionite - iron out

    The product Iron Out contains Sodium Dithionite (smaller amounts of Citrix acid and some ph stabilizers)

    The companies FAQ specifically says they don't recommend it for use in a pool although it can be used for iron stain removal in an empty pool

    Mostly curious but what would be the chemical problem or end result from using this vs ascorbic or oxalic acids in stain removal

    Now while I have a BS in molecular biology I'm a surgeon by nature so it's been awhile since I've looked at a lot of formulas but as far as I can tell the reduction of iron oxide would the leave you with some sulfates or sulfites, the only worrisome product might be Thiosulfate but that would seem to quickly react with chlorine to get back to sulfate.

    Seems this chemical is commonly used in water treatment so I'm curious if anyone with a better knowledge of chemistry has any thoughts

    The product certainly works well, see my other post where I removed some local iron staining but didn't add it to the pool at large

    While were talking about it what is the end product of using citric or oxalic acids I assume since they are organic acids they eventually get oxidized by the chlorine down to harmless end products
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    Melt In The Sun's Avatar
    Join Date
    Oct 2009
    Tucson, AZ

    Re: Sodium dithionite - iron out

    This is just a guy's opinion, there are people on this forum with much more chemistry chops than myself.

    OK, disclaimer over. I think it would work, but would end up being quite expensive. Using that to spot treat is one thing, but dumping enough in your pool to get an effective concentration would require quite a large amount. Not sure how the cost compares directly with ascorbic or citric acid.
    11,200 gal, Pebble-Tec; Tristar 2-speed 1hp - Swimclear 325 ft2 cart - SWG - A & A in-floor cleaner - Heat pump. For the poolside cooking, a Yoder Wichita and a Big Steel Keg!
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    Join Date
    Mar 2007
    San Rafael, CA USA

    Re: Sodium dithionite - iron out

    It seems like sodium dithionite would be OK to use. The end product of this reducing agent is sulfate (via sulfite).

    Citric acid in water is mostly citrate ion and gets oxidized to acetonedicarboxylic acid (acetonedicarboxylate ion) and then further to malonic acid also producing chloroform and carbon dioxide (see this paper). Perhaps the end product of chloroform (a trihalomethane) is why the product that contains some citric acid is not recommended for use in chlorinated pools.

    Oxalic acid in water is mostly oxalate ion and gets oxidized to carbon dioxide.

    Ascorbic acid (vitamin C) has the end product of dehydroascorbic acid. Since this product does not have any nitrogenous sites nor methyl ketone or carboxyl or sulfur sites, it does not get readily further oxidized by chlorine. The dehydroascorbic acid will mostly just stay as is in water as a dissolved organic substance.
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