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97% Sulfuric acid+ KI


budullewraagh

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Possibly some bromide contamination in your potassium iodide. Bromine is VERY volatile, much more so than iodine, so if any was generated it would quickly evaporate into the distinct, red/brown/orange vapor.

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erm... WHY did you use 97%?

 

50% would have been perfect! you actualy Forced a reaction that should have required heat at 50%, it dehdrated water of crystalisation in the KI and spontaniously reacted. Dumb! (but funny LOL) :))

 

there`s no Bromine, just HI(g) and yes there will be some H2S in there as the lot decomposed with a few side reactions. don`t worry about that tho, you`re alive enough to have typed this, you`ll live :)

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Well, I wouldn't be so sure about saying that there's 'no' bromine. Depending on the purity of the KI that was used, there's a very good chance that there would be some KBr contamination. The H2SO4 would undoubtably oxidzie the Br- into elemental bromine. So some of the red/brown/orange gas may have been bromine vapor.

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so i was sort of right about the HI, i wasnt sure because ive only seen that reaction done with sodium iodide, but there all alkali metals! the whole reaction hasnt worked for me before though to make pure iodine, the HI is supposed to be oxidised by left over sulphuric acid, so i should have iodine n SO2? any tips on how to get it right, im not sure how pure 'ebay' samples are.

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I`m familiar with that method too, such as here: http://www.webelements.com/webelements/elements/text/I/key.html

 

KI works just as well, and I srongly suspect that much of what was considered large amoungs of H2S was infact SO2 also, as I said, there are quite a few side reactions that take place :)

 

from the HI stage, I`de THEN do the Cl gas method, taking off the I(g) sublimate as it`s produced.

 

it`s just personal prefs though :)

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Here's a quick question. Would it be possible to take a solution of iodide ions and add hydrogen peroxide to it to oxidize the I- back to I2? If this could work with the store-bought 3% H2O2, that might wind up being a safer, easier method of manufacturing iodine.

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Hmmm. I'll have to give that a test. I'll try and pick up some KI sometime soon and put some crystals of it into some H2O2. I know that it will cause the rapid decomposition of the peroxide into water and oxygen, but I'll try and see if the solution starts turning colors. If that does work, then it would be a fantastic way of producing iodine in the home. (Though I'm now starting to think that it's not that simple since if it was, people would have already known about it). Let's see what google has to say. :D

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Okay. Under normal conditions, very little, if any iodine will be formed since the first step in the reaction is the formation of the IO- ion which then further reacts with the peroxide forming the I- ion again. So with just hydrogen peroxide and KI, the KI is only a catalyst. However, if the reaction medium is acidic, pure iodine is formed. I've heard that you really only need 1.0 molar sulfuric acid, though I believe that acetic acid would work as well. So maybe one should try dissolving some KI in some concentrated vinegar, and then adding some regular H2O2 to that.

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begs the question where the Hydrogen goes though?

perhaps atmospheric oxygen acts as a base and accepts the hydrogen

 

i think i'll finish that reaction later today. as it is, the solution looks brominated; i believe i can see aqueous tribromide/triiodide anions as well as aqueous elemental iodine (only aqueous because of presence of aqueous potassium iodide). as it is i think it has been acidified enough so i'll just add the 35% hydrogen peroxide and let it be done. good idea? oh, and i think i'll do it outside this time so as not to breathe in anymore bromine:\

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