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Sodium Iodide {Na+ {I-}
An overlooked source of free iodine
In the HI/RP reaction using either the dry(P/P) method or the reflux
method, most of the iodine is recoverable.
NaOH or suitable base is added to the finished reaction mixture, making the
meth molecule non-polar{oil soluble).
The oil layer and meth are separated from the lower polar layer.
If the polar(water) layer is left to cool for a while, long thin white
crystals will form in this discard fluid.
The crystals are Sodium Hydroxide(NaOH) and Sodium Iodide .
Push /pull tanks
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In the P/P method the push /pull tanks contain most of the Iodine as HI, but
it very dilute so adding peroxide and bleach will precipitate out the iodine
crystals I2. The I2 crystals are very slightly soluble in water and can be
washed by shaking with distilled water , then decanting the distilled wash
water as waste, and eventually collecting the solid I2 crystals in a filter.
NaI + H+ <--> HI + Na+ (acid/base, Lowry-Bronstead)
I2 + 2e- <--> 2I- (Redox)
Reaction waste alkaline water
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In the reaction flask the fibrous white Sodium iodide cryatals can be
collected by decanting off the alkaline waste water fluid.
Then adding dilute sulfuric acid (carefully) to dissolve the fibrous White
crystalline NaI, then adding peroxide and bleach to precipiate the much
DARKER I2 crystals, when an electron pair is added to 2I-.
Sodium Iodide
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In the P/P method the amount of iodine in the discardable polar layer is
variable.
However if the reflux method was used with a condenser as a cooling tower,
most all the iodine is in the discardable alkaline water (polar layer) from
the reaction. This often discarded fluid is a source of much potentially
recyclable iodine.
In the past I have flushed these crystals thinking they were merely
contaminated NaOH. but once it is realized that they are mostly the
considerably more valuable NaI recycling becomes worthwile. Most of the
iodine is still present as Sodium iodide and is collected the same way it is
collected above.
In fact all the iodine should be re-cyclable and collectablem unless it
escaped and a small amount is famous for staining walls. At least 50% is
typically easily recoverale and probably much more will be a bonus for adding
a little acid and household bleach, then washing it with water, finally
collecting it in a filter and it is ready to use again. It is quite wet so
don't add much water to your reaction if using the dry(P/P) method .
Compensate for the water contamination to iodine that is not dry, by
adding 15% more iodine by weight to the reaction, than is called for, or it
may be short of iodine and the reaction may suffer.
Worlockium
http://www.geocities.com/CapeCanaveral/Runway/4986/two/start.html
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