[lordofdarkness]

Is their anywat to extract Iodine from seaweed?

[xiankai]

well yes, but i dont know why u need it for. the process isnt really safe, and another of the products formed is very dangerous

[hmx9123]

I believe it is the industrial process.  I think it's mentioned in the 'elements' section of the CRC.

[Ian Donaldson]

I've been interested in extracting iodine from seaweed since my schooldays 45 years ago, and have now got round to trying it out.  Old chemistry books and Victorian encyclopaedias give the details.  The dry process involves burning seaweed to ash. This ash is known as kelp - perhaps as it was originally derived from kelp seaweeds.  The best seaweed is supposed to be Laminaria - these are long leather-like fronds - 4 to 6 feet long, flat and up to 5" wide, brown in colour, but I expect any brown seaweed will do.  The best ash was supposed to have a purple colour - I don't know why this should be.  The ash is treated with strong sulfuric acid - concentrated sulfuric acid is an oxidising agent.  By heating or boiling the mixture, Iodine is liberated, and distills off as beautiful violet vapours. These were condensed in earthenware bottles known as udels - the old diagrams show them to look like wine bottles laid in a long line, neck to base - the wide base having a hole in it large enough for the neck of the preceeding bottle. Iodine condenses as black shiny plates inside these bottles and can then be scraped off when cold.   The process is not dangerous, so long as you take care with the concentrated sulphuric acid.  (To dilute it never add water to the acid - it will boil and splatter about. Always dilute the conc. sulfuric acid by adding the conc acid slowly to cold water.) This acid probably needn't be as as stong as the acid available nowadays - 95  to 99%.  In Victorian times the strongest sulphuric acid easily available was only about 70%. The iodine crystals will stain your skin brown.  It is corrosive but not dangerously so - as a boy I used to burn off my warts by taping a small crystal of iodine on top of the wart and leaving it on overnight.  Partington's "Text-book of Inorganic Chemistry" gives reasonable details.  My copy is dated 1950, published by Macmillan and Co in London.  It gives details of the wet process too.   I'm planning to try out the dry process soon, and would be  interested in your comments.   Cheers!   Ian Donaldson, Bristol, UK.

[Ian Donaldson]

As a post-script, I should state that the yield is very small - I expect to get only a few milligrams from a kilogram of ash.   Seaweeds contain a lot of water, and large wet fronds when dry shrink to the size and weight of a feather.   The only nasty by-product I expect to get is fumes of hydrogen chloride from the residual salt in the seaweed.

[Borek]

One thing that I don't like about the process you described is burning of the seaweed. I wonder - remembering the volatility of iodine - if it will be not mostly lost at this stage.

[jdurg]

Why would the iodine be stored as elemental iodine in the seaweed?    Chances are, the iodine is present as the iodide salt or some other complex that is most certainly not volatile.  

[Borek]

If it is in form of iodide you are right, but I suppose it is rather in form of some organic compounds - and elemental iodine as a product on their thermal decomposition will not raise a brow.

Chances are final yield is high enough to be not afraid of losses at first stage.

[Ian Donaldson]

Borek - you are quite right - Victorian texts mention a considerable loss  of iodine when the seaweed  is burnt.  To get round this the Scandanavians invented  a wet method of extraction.  I plan to try the dry method, but burning the seaweed on a low fire.   I'm thinking of doing this sometime in a closed reaction vessel too, and condensing the vapours,  but I  suspect my Pyrex glassware will not take the  heat. It will have to be porcelain, stoneware or simply tin cans with iron piping.  A very full description is given in Tomlinson's "Cyclopaedia of Useful Arts" published sometime after 1850. The process using sulfuric acid works better if manganese dioxide is added as an oxidising agent.  Courtois, the French chemical engineer who discovered Iodine  in 1811 was  simply trying to get rid of an encrustation on his soda vessels by washing it with sulfuric acid.   Beautiful violet fumes evolved - the iodine sublimes easily with gentle heat. He'd been using seaweed as a source of sodium carbonate.  Some  texts describe  him as a saltpetre manufacturer, some  as a  soap maker - perhaps he did both.
Cheers!  Ian Donaldson, Bristol, UK

[lordofdarkness]

Back!!
I know theres some anstetic solutions containg a compound with iodine, Could i use electrolysics then?

[billnotgatez]

No entry found for anstetic