unexplained yellow color in acid-iodine-sulfite system-literature help

From: Mohammed Farooq (farooq_w_at_hotmail.com)
Date: 07/09/04 

Date: 9 Jul 2004 10:16:07 -0700

Recently Wilco posted a problem in a seemingly simple reaction:
To a solution of potassium iodide acidified by dilute sulfuric acid or
HCl is added sodium metabisulfite (NaHSO4) solution, immediately a
lemon yellow color is developed on mixing.
I repeated his experiment and found the same and speculated that it is
     tri-iodide ion which is causing this color:
The problem:
The Vis spectrum of this solution shows only a single peak at 346 nm,
matching very closely to peak of known tri-iodide solution at 347 nm,
suggesting that it is indeed tri-iodide, but this yellow solution is
not decolorized by sodium thiosulfate, no matter how much of it is
added. I did not take its derivative spectrum to resolve overlapping
peaks, if any, which suggests that it not *simple* I3(-).

Searching more about this reaction I came across a reference in
*Inorganic Chemistry*.
"Non-Metal Redox Kinetics: Reactions of Iodine and Triiodide with
Sulfite and Hydrogen Sulfite and the Hydrolysis of Iodosulfate", Yiin,
B. S.; Margerum, D. W. Inorg. Chem. 1990, 29, 1559-1564.

which I think might explain Wilco's problem and solve the riddle which
so much perplexing me.

I would be grateful if someone takes a look at this article in his/her
spare time because our library does not have recent issue of this
journal and ACS website does not provide abstracts to non-suscribers
buying that article for $25 is out of my reach.

Relevant Pages

  • Re: unexplained yellow color in acid-iodine-sulfite system-literature help
    ... > Recently Wilco posted a problem in a seemingly simple reaction: ... > The Vis spectrum of this solution shows only a single peak at 346 nm, ... I did not take its derivative spectrum to resolve overlapping ... Little or no signal change with time was observed ...
    (sci.chem)
  • Re: unexplained yellow color in acid-iodine-sulfite system-literature help
    ... > Recently Wilco posted a problem in a seemingly simple reaction: ... > The Vis spectrum of this solution shows only a single peak at 346 nm, ... > matching very closely to peak of known tri-iodide solution at 347 nm, ... > Sulfite and Hydrogen Sulfite and the Hydrolysis of Iodosulfate", Yiin, ...
    (sci.chem)
  • Re: Effect of Reactant And Product Numbers
    ... where a is the reactant number, b is the product number, and n is the ... As the reactant number increases, e.g. the reaction 2A+e=B, its ... its peak becomes more lower and broader. ... half-peak width 0.055 V in the one-electron reaction. ...
    (sci.chem)
  • re: Effect of Reactant and Product Numbers
    ... For a charge reaction ... If you change the reactant and/or product number of charge ... As the product number increases, e.g. the reaction A+e=2B, its ... its peak becomes more lower and broader. ...
    (sci.chem)
  • Effect of Reactant And Product Numbers
    ... For a charge reaction ... If you change the reactant and/or product number of charge ... As the product number increases, e.g. the reaction A+e=2B, its ... its peak becomes more lower and broader. ...
    (sci.chem.electrochem)
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