Iodine & Iodide

Discussion in 'General Discussions and Advice' started by Warr7207, 18 Oct 2008.

  1. Warr7207

    Warr7207

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    What is difference between iodine and Iodide?

    Sorry i did Google it but got these answers, which i am not sure are 100%.

    " Best Answer - Chosen by Asker

    Hi,

    I think that iodide is an ion, i.e. it has reacted with a metal so it has gained electrons and is now a negative ion.

    Where as, iodine is just a neutral atom.

    :)"

    Can both these be used in Marine Tanks ?
     
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  3. Reef Maniac

    Reef Maniac MASA Contributor

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    Warr, I hope you don't mind, but I think it will be better to discuss this interesting topic in it's own thread, so I moved it here.

    The quote is correct, but that does not make it easier to understand :whistling:

    Iodine (I) is an element, the same as nitrogen (N) and phosphorus (P). Iodide (I-) and Iodate (IO3-) are ions of iodine, just the same as nitrite (NO2-) and nitrate (NO3-) are ions of nitrogen, and phosphate (PO4-) is an ion of phosphorus.

    It is my understanding (chemical boffins, please correct if I'm wrong...) that the "...ite" and "...ate" at the end of these names indicate the level of oxidation of the elements, with the "...ate" referring to the highest, most easily accessible oxidation state of the ions. Thus iodate and nitrate are the most oxidized common forms of iodine and nitrogen.
    We probably all know the term “denitrification.” This process happens in regions of the aquarium where the oxygen concentration is low (anaerobic), such as for example, within live rock and in deep sand beds. Iodide is converted to iodate in the same type of (anoxic) processes.

    The total concentration if iodine (and all it's ions) is approximately 0.06ppm, with approximately two-thirds being iodide and one-third being iodine. This concentration changes with depth, with the iodide ion concentration decreasing and the iodate ion increasing as the water becomes more anaerobic.

    As far as I know (marine biologists and bio-chemists, please confirm...) marine organisms which uses iodine (and not many do...) mostly take up iodide and iodate, and only a few species are capable of using iodine (for more info, read this excellent article by Dr. Randy Holmes-Farley). Fortunately, elemental iodine changes quite rapidly into iodide once added to our tanks.

    Inorganic (elemental) iodine is rather insoluble in water, and commercially available iodine additives (and DIY additives such as Lugols) contain a large proportion of iodide in addition to iodine.

    Hennie
     
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  4. Warr7207

    Warr7207 Thread Starter

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    Great explanation Hennie, thanks :)
     
  5. Tommo

    Tommo

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  6. Reef Maniac

    Reef Maniac MASA Contributor

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  7. Tommo

    Tommo

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    LOL sorry mate
     
  8. freedom

    freedom

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    Hi,
    I've just started to introduce soft corals to my tank and I've read that soft coral, polyps and mushrooms love iodine. I accidently bought iodide. Question ?... Is it the same product (element) ? Does iodine + oxygen = iodide ? Therefore, the same ?

    Thanks for answering,

    Freedom
     
  9. Reef Maniac

    Reef Maniac MASA Contributor

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    Well, as stated in the second post above:

    I would caution against the liberal use of any iodine additive if one cannot test accurately for this in the tank water. It is true that things like skimmers and ozone remove iodine (and it's ions...) from the water, but normal feeding of the tank, and doing regular partial water changes, replaces much of this again.

    As stated in the article referred to above, there are actually not many organisms which have been proven to benefit from increased iodine levels. Something else to consider, is that iodine is pretty insoluble in water, and other chemicals are needed to make these solutions - things such as alcohol. Apart from adding an amount of carbon (which could cause cyano blooms), we also do not have any indication of what other impurities are contained in this alcohol (or whatever else is used to make these solutions). If alcohol is distilled in a copper still (as happens in industrial processes), one could thus be inadvertently increasing the copper concentration in our tanks - and as everyone should know, copper is a very toxic substance for most marine organisms.

    Personally, I think I'm safe to say that I have one of the largest leather corals in South Africa (had it for some 8-10 years in my tank), and I run a large skimmer AND ozone, and have never used any iodine additives (well, OK - I did probably use one bottle way back when I started my tank, as I did not know any better at that time...).

    Hennie
     
  10. seank

    seank

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    Ask Hennie Landman about this (Reef Maniac) ;)
     
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