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Electrolysis of potassium iodide to form iodine
To electrolyze a potassium iodide solution. Electrolysis is a process by which a chemical reaction is carried out by means of the passage)of an electric current. As the reaction proceeds iodide is oxidized at the anode (negative) while water is reduced at the cathode (positive).
2I--->(aq) I2(s) + 2e-2H2O(l) + 2e- --> 2OH-(aq) + H2(g)
net reaction: 2I-(aq) + 2H2O(l) -->I2(s) + 2OH-(aq) + H2(g)
The cathode will be recognized by bubbles (H2) on the electrode and pink phenolphthalein indicator from hydroxide production. Phenolphthalein turns pink in the presence of base and clear in the presence of acid. A slight yellow/brown color to the water around the anode may be observed. This is due to a small amount of iodine being dissolved in the Water.
Materials:
alligator clips (4)
9V battery
insulated wire
solid potassium iodide
spoon
carbon electrodes ( led removed from two pencils )
shallow bowl (clear glass or white plastic a beaker would be perfect)
white paper
Procedure:
Add some KI (about the size of your baby fingernail) to the bowl, fill it half full with water and stir until the KI is dissolved. Put a white piece of paper under the bowl if it is a glass bowl.
Connect the wire to the alligator clips.
Clip one alligator clip to the tip of the pencils. ( Remove the led from the pencils for use as electrodes ).
Attach the other ends of the wires to the battery.
Place the electrodes in the bowl so that the pencil tip is in the solution.
Observe the electrodes for evidence of reaction. You will observe a pink color to a red color with a saturatted solution.
To produce iodine for collection you would want to use a saturated solution of sodium iodide.
How much current will be required to liberate 10 g of iodine from potassium iodide solution in 2 hours ? (Eq. wt. of I2 = 127.0)
[ Ans. 1.06 amp ]
[source: http://www.geocities.com/dcarrd2000/iodine_info_101.html (http://www.geocities.com/dcarrd2000/iodine_info_101.html)
]
There's another methods by bubbling clorine gas through a H2O/KI or NaI solution that also looks doable, and good fun! :)
But nothing as simple as the electro method above.
Will try it asap, can't wait! :) 8)
Got the URL from the nice bee in the currect seaweed/iodine thread yesterday, and found that further down the page.
I wonder if any water soluble iodide would do? this may be a non-issue because I don't think the two mentioned would be difficult to find but ill ask anyway for personal interest.
pROcon
don't call me...I wont answer, or call you back.
Urushibara
Or am I wrong about Iodine coming out of the salt with the addition of HCl and H2O2... It makes sense to me - if chlorine gas pulls KI apart and leaves I2, though it progresses further, which makes the HCl method better. The standard tincture extraction works even better, because the HCl preferentially substitutes for the I and makes KCl and the I2, as the KCl forms, the I becomes less soluble and crystallises out of solution. What function does the H2O2 perform?
Nope, your spot on.
Okay so we have the HCl containing the NaI/KI, then some H2O2 added to the HCl/NaI or KI solution...the H2O2 gives off one of it's Oxygens to the HCl (which is at that point liberated of it's Clorine molecule). So the HCl becomes H2O, and the H2O2 which has lost an O also becomes H2O.
The clorine as you said, liberates the I from the iodide, to become I2, elemental iodine, which is insoluble in water, so then it's filtered out! :) 8)
Learnt that last night from I think Osmium! After I posted about the electrolysis, (which I better note is better suited to NaI, as opposed to KI, as it says further down on the URL I sent, but they could both be used).
Hope this helps!
pROcon :)
don't call me...I wont answer, or call you back.
Or am I wrong about Iodine coming out of the salt with the addition of HCl and H2O2
You are not wrong. Post 280939 (https://www.thevespiary.org/talk/index.php?topic=6012.msg28093900#msg28093900)
(terbium: "Re: KI crystals", Chemicals & Equipment)
It makes sense to me - if chlorine gas pulls KI apart and leaves I2, though it progresses further, which makes the HCl method better. The standard tincture extraction works even better, because the HCl preferentially substitutes for the I and makes KCl and the I2, as the KCl forms, the I becomes less soluble and crystallises out of solution. What function does the H2O2 perform?
Even though your reasoning is. Post 213974 (missing)
(terbium: "Re: OTC Iodine synthesis", Chemistry Discourse)