plante1999
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Iodine extraction using sodium nitrite (pictures)
Iodine is used in many reactions, is a common reagent, and I believe most people know its many uses. Nitrite ion was used to oxidize the iodide
instead of the other common oxidizing agent due to scientific curiosity. Nitrogen is produced as well as iodine in acidic condition. A strong excess
of nitrite was used to break the triiodide ion and to clearly show the endpoint of the reaction.
6KI + 2NaNO2 + 4H2SO4 -> Na2SO4 + 3K2SO4 + N2 + 3I2
Reagents:
Sodium nitrite, reagent
Potassium iodide, reagent
Sulphuric acid 30%, technical
Sulphuric acid 93%, technical
30 g of potassium iodide and 8 g of sodium nitrite where dissolved in some water, and slowly the acid solution was added, but it was found that both
solution where too concentrated, so they where diluted to slow the reaction a bit. A transparent gas evolution was evident until near to the end of
the reaction, where the gas produced was brown. Foam of iodine was made at the end due to the triodide decomposition, precipitating a lot of iodine.
The solution was filtered, and the still wet iodine was put into 50 ml of concentrated sulphuric acid while in an ice bath (actually a snow bath,
outside). The mixture was heated on flame to melt the iodine, the sulphuric acid was decanted, and the solid piece of iodine washed with water.
Strong odors
The procedure was less messy then most procedure I had used in the past, and less exothermic, but it was far from perfect and still extremely messy.
The salts mixture:
http://i1103.photobucket.com/albums/g469/plante1999/DSC00258...
The solution:
http://i1103.photobucket.com/albums/g469/plante1999/DSC00259...
The reaction:
http://i1103.photobucket.com/albums/g469/plante1999/DSC00260...
http://i1103.photobucket.com/albums/g469/plante1999/DSC00262...
Sulphuric acid melting:
http://i1103.photobucket.com/albums/g469/plante1999/DSC00263...
The final product:
http://i1103.photobucket.com/albums/g469/plante1999/DSC00267...
I never asked for this.
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Pyro
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yet another nice article, why don't you put these in prepub?
and I suggest you post you pictures like this:
<img src="http://i1103.photobucket.com/albums/g469/plante1999/DSC00259_zps47889637.jpg" width="800" /> using ''insert an image. (7 from the left
on the toolbar)
Your H2SO4 is a lot less dark then mine when I melted I2, was your product dry before you put it in?
<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: reduced
image size(s)]
[Edited on 30.12.13 by bfesser]
all above information is intellectual property of Pyro.  |
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plante1999
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I could put them in the prepub, yes...
I would need to re size all of the pictures and it would take a lot of time with the method I use, so I give the links instead. My product was not dry
at all, quite moist and much like a paste.
I never asked for this.
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Pyro
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thats odd, My I2 was also a paste and when adding it to H2SO4 (crystal clear 99,99%) it turned black.
all above information is intellectual property of Pyro. |
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plante1999
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Maybe the difference is in the iodine, anyhow, I'm planning for the next part, methyl iodide.
If anyone feel like making a prepub. out of my last few preparation, he his welcomed to, but I don't think I will.
I never asked for this.
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blogfast25
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Quote: Originally posted by Pyro  | yet another nice article, why don't you put these in prepub?
and I suggest you post you pictures like this:
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Please specify photo size, see here:
http://www.sciencemadness.org/talk/faq.php?page=messages#7
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bfesser
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Keep embedded images below 800 pixels in width. I've explained this before; you can search for it if you like.
For images 800px or wider, use this code: | Code: | <img src="image_url_goes_here" width="800" /> |
If already resized below 800px, you may omit the width attribute.
[edit] plante1999, do you have any references or links to add? I know, for instance, that the fusion under
H<sub>2</sub>SO<sub>4</sub> was recently mentioned in another topic.
[Edited on 30.12.13 by bfesser]
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Morgan
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It might be fun to mold pellet-sized pieces of iodine and drop them onto a Leidenfrost maze, if they would melt into a bead and skitter along the
path. A violet vapor trail would enhance the effect although aluminum probably wouldn't be the best hotplate material for iodine.
When Water Flows Uphill
http://www.youtube.com/watch?v=zzKgnNGqxMw#t=3m3s
EFECTO LEIDENFROST - VIDEO 12
http://www.youtube.com/watch?v=K_JwoMVYxqk
The Leidenfrost effect.
http://www.wimp.com/leidenfrosteffect/
Tidbit on theory
"The ratchet temperature (350 oC) is much higher than the Leidenfrost temperature of ethanol (200 oC). The length and
the height of the teeth are 1:5 mm and 300 um, respectively [6]."
"Dry ice indeed levitates (Fig. 6) and moves in the same direction as Leidenfrost drops and
is driven with a constant force. Hence, even Leidenfrost solids self-propel and we conclude that
the motion is not necessarily related to deformability of the liquid, which suggests that vapour
production is the primary cause of motion. If a drop is deposited on a
at surface vapour escapes isotropically but the presence of a ratchet breaks the symmetry of
the substrate and directs the vapour flow."
http://mafija.fmf.uni-lj.si/seminar/files/2011_2012/leidenfr...
[Edited on 30-12-2013 by Morgan]
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plante1999
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Thanks bfesser for the tip, I might have a few references to put yes, they will take time to find as my original source for melting iodine under H2SO4
was from a 2 year old thread or so. For the nitrite reaction though, that was hypothesized based upon my personal knowledge of chemistry.A few other
could be added too.
Morgan, that would be too messy and smelly for me, and I don't recomend anyone to do it.
I never asked for this.
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Morgan
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I don't think it would be that hazardous to drop a few small iodine pellets on the maze I mentioned. If you watch this video around the 19 second
mark, you can see how small the apparatus really is and mere tiny droplets of water are being use. I suppose you could put a dome over the maze, take
it outside, or use a fume hood without too much danger. The iodine might etch the aluminum though. From earlier videos I imagined the maze much larger
because there wasn't a reference shot.
Physics Students a Maze With Leidenfrost Effect
http://www.youtube.com/watch?v=x1JddRZARk8
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HeYBrO
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Here is a post that mentions the H2SO4 purification http://www.sciencemadness.org/talk/viewthread.php?tid=22658#...
this thread also mentions using a nitrite salt http://www.sciencemadness.org/talk/viewthread.php?tid=22182#...
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plante1999
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I won't reference documents I did not used, I'm against that. So I can't put the first link. As for the second, I know I may look a bit pretentious
time to time, but I won't reference myself...
I never asked for this.
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HeYBrO
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You won't reference yourself eh?  I don't know where you got pretentious from i
just thought the links may be helpful. Anyway, great write up Plante!
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AJKOER
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While this is an interesting preparation of I2 from KI, I think I will first try adding a strong acid to a dry powder mixture of KI and 2Na2CO3 ·
3H2O2 (Sodium Percarbonate, commercially available as OxiClean, see http://en.wikipedia.org/wiki/Sodium_percarbonate ), the latter being easily available. I purchased a generic substitute (not the OxiClean brand),
which was basically just the percarbonate absent perfumes,...
Apparently, H2O2 reacts with Hydrogen iodide (created in-situ) liberating Iodine (see, for example, http://www.kbcc.cuny.edu/academicdepartments/physci/pl/chm12... ), the quoted reaction being:
2 KI(aq) + 2 HCl(aq) + H2O2 (aq) --> I2 (s) + 2H2O (l) + 2 KCl
So, the reaction via Sodium Percarbonate would be:
6 KI(aq) + 10 HCl(aq) + 2 Na2CO3. 3/2H2O2 (s) --> 3 I2 (s) + 8 H2O (l) + 4 NaCl + 2 CO2 (g) + 6 KCl
When I try this, I will report back on my opinion of how messy and exothermic.
If this alternative method is not that good, I welcome comments.
--------------------------------------------------------------
[EDIT] I believe your reaction can also be performed as:
2 NaNO2 + 2 NaI + 2 H2SO4 → I2 + 4 NaHSO4 + 2 NO (see http://wiki.answers.com/Q/How_is_Nitrogen_Oxide_Formed )
versus your take:
6KI + 2NaNO2 + 4H2SO4 -> Na2SO4 + 3K2SO4 + N2 + 3I2
So, one can use less H2SO4 than you have indicated as:
H2SO4 (conc.) + Na2SO4 = 2 NaHSO4 (40° C) (see http://www.allreactions.com/index.php/group-1a/natrium/sodiu... )
However, note the gas formation cited is not your safe N2, as you indicated, but the colorless NO (which, with air, creates the highly corrosive NO2,
a reddish-brown gas which agrees with your comment "where the gas produced was brown").
[Edited on 4-1-2014 by AJKOER]
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AJKOER
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Here is a better source (link: http://www.ut.ee/ARFA/fkeemia/3kur_syg.pdf , search on 'HNO2') that confirms my assertion that Nitric oxide is formed. Quoted reaction chain:
"NaNO2 + HCl --> NaCl + HNO2
KI + HCl --> KCl + HI
2 HNO2 + 2 HI --> I2 + 2 NO (g) + 2 H2O"
--------------------------------------------------------
So with H2SO4:
NaNO2 + H2SO4 --> NaHSO4 + HNO2 (assuming no strong heating otherwise K2SO4 is formed in place of the bisulfate and the Nitrous acid likely
decomposes as well)
KI + H2SO4 --> KHSO4 + HI
HNO2 + HI --> 1/2 I2 + NO (g) + H2O
Net reaction:
NaNO2 + KI + 2 H2SO4 --> NaHSO4 + KHSO4 + 1/2 I2 + NO (g) + H2O
Now, I would suggest an excess of KI as in the presence of O2, NO2 forms, which with water vapor creates HNO2 and HNO3, and per the reactions:
2 NO + O2 --> 2 NO2
2 NO2 + H2O --> HNO2 + HNO3
6 KI + 8 HNO3 --> 6 KNO3 + 2 NO (g) + 3 I2 + 4 H2O ( see http://bigdargon.blogspot.com/2009/05/chu-k.html )
any formed Nitric acid (and new Nitrous acid) can be converted into NO gas and Iodine. Put differently, one colud plan to use less H2SO4 as with the
addition of oxygen, acids to move the reaction forward are created.
[Edited on 6-1-2014 by AJKOER]
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