SimpleChemist-238
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Isolation of Iodine From SeaWeed
The discovery of iodine by Bernard Courtois was accomplished by the extraction of seaweed. In sea water 14 cubic feet of water contain only 1g of
iodine ( I believe that is 234345706800g on earth according to Google). In seaweed the concentration is about 3% by mass.
The extraction is simple.
Collect the wanted amount of seaweed from a nearby beach and wash it in fresh water so that most impurity's are removed.
Let the SW dry outdoors in sun light for 1 week and prepare a crucible with the correct volume for the seaweed.
Incinerate it until there is a blackish white powder has replaced the it.
Remove the ash and place it in twice its weight in water and sir for 1 hour so that salts may be dissolved.
Filter and biol the solution to a concentrated state. Add sulfuric acid to it and cool.
Next add a strong oxidizer (Calcium Hydrochlorite , H2O2) and stir with cooling. Place the Container on a heating source and heat so that iodine vapor
will be created and collect.
Recrystallize iodine when finished.
Chlorine and bromine will also be produced.
[Edited on 15-3-2015 by SimpleChemist-238]
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Magpie
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peach did this extraction if you care to look up his work on this forum:
http://www.sciencemadness.org/talk/viewthread.php?tid=12193#...
[Edited on 15-3-2015 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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SimpleChemist-238
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Thanks, I did not try to double post, I searched iodine and seaweed before this and did not find it.
We are chemists , we bring light to the darkness. Knowledge to ignorant, excitement to the depressed and unknowing. we bring crops to broken fields
and water to the desert. Where there is fear we bring curiosity.
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Magpie
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I had trouble finding it myself - I just knew it was there somewhere. 
The single most important condition for a successful synthesis is good mixing - Nicodem
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SimpleChemist-238
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Have you attempted it?
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Magpie
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No, fortunately I still have some left from the days, not so long ago, when you could buy 7% solution for the treating of horse hooves, etc.
Extracting it from seaweed looks like way too much work. There's got to be easier ways to get a little I2.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Derek McOlund
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Bromide from Seaweed
"Next add a strong oxidizer (Calcium Hydrochlorite , H2O2) and stir with cooling. Place the Container on a heating source and heat so that iodine
vapor will be created and collect.
Recrystallize iodine when finished.
Chlorine and bromine will also be produced."Bromine will be produced, but can it be captured and turned
into NaBr? Do you know the concentration of naturally occuring bromide in seaweed?
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Chlorine
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Quote: Originally posted by Magpie  | No, fortunately I still have some left from the days, not so long ago, when you could buy 7% solution for the treating of horse hooves, etc.
Extracting it from seaweed looks like way too much work. There's got to be easier ways to get a little I2. |
Agreed, extracting iodine from seaweed isn't exactly practical, although it's an enjoyable project for a slow day.
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Harristotle
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Different species concentrate it to different degrees.
I have found the brown algae (Ecklonia) are best, but never really extracted much as this was just an experiment to see what was best. The trouble
with those is that they hang onto their water the longest due to high alginate concentration.
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phlogiston
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I tried it, using a few kg's (wet, including adherent water) of Fucus vesiculosus L. (bladderwrack). The yield was visible but small, probably no more
than 50 mg (did not bother to collect and weigh it from the suspension after oxidation to its elemental form)
Youtube channel Cody's Lab has an interesting video, where he obtains a surprisingly large amount of iodine from merely a bucket of seemingly randomly collected seaweed, which
triggered me to try it. Although F. vesiculosys is supposed to be relatively rich in iodine (there is a book online somewhere listing the iodine
content of different seaweeds.), my yield was much, much lower.
[Edited on 30-11-2016 by phlogiston]
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Marvin
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When I tried, a long time ago now, after adding acid and peroxide all I got was a golden brown colouration in the liquid. I was not at all choosy
with the seaweed, I just grabbed 2 carrier bags full and burnt them when I got home. 3% of seaweed weight sounds far too high. Maybe 3% of ash, if
you use just the right kind of seaweed. I'd be interested to know if much iodine is lost during the burning and if recrystallising the ash is
worthwhile to decrease the acid needed.
I'd love to say I learned a lot, but I don't think I did, I pretty much chalked it up as a fail. Wash the salt off the seaweed or it won't burn, let
it dry very well, which seems to need full sunlight. Don't plan a retirement off the income.
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