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Science Forum Index » Chemistry Forum » Iodine/Iodide Chemistry...
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 Posted: Tue May 06, 2008 6:19 am |
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Guest
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In an attempt to precipitate iodine, I added sodium hypochlorite
(NaOCl) to alkaline (pH ~13) aqueous potassium & sodium iodide (KI &
NaI). At first, iodine appeared to precipitate, but then the
precipitate turned white. Now, I have a milky white layer, which
appears to be fluid, covered by clear solution. Over time (days), the
milky white layer shrinks from ~99% to ~10% of the total volume, and
the clear layer grows. (As I recall, the solution then turned
completely clear, but further experimentation has clouded my recall).
Also, I should probably add that the original iodide solution was
probably contaminated with calcium, copper, tin and other metals.
Whereas, I filtered the solution of what appeared to be mostly or
completely copper hydroxide, of course hydroxides are slightly
soluble at that pH (on the order of several mg/L for copper hydroxide,
for example).
I believe my mistake was not lowering the high pH of the original
iodide solution. Can anyone explain the reactions that I'm seeing?
What is the milky white layer? What would be the best pH for
precipitating the iodine with sodium hypochlorite? |
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