Alright everyone!
Welcome back to Cody's Lab
So I was recently challenged...
to extract iodine from iodized salt
There's not a lot of Iodine here, since iodine is a
micronutrient that you don't need in very large amounts.
But it should be rather doable.
One thing I am going to note before I start,
This is not gonna be very practical way of getting iodine, It would be far cheaper and easier just to buy
Iodine or even sodium iodide. Now let's have a look at the label real quick
Zoom in here, so it has salt
Obviously it's a can of salt
Sodium silicoaluminate. So that's your anti-caking agent
dextrose
ahh a little bit of sugar in there; that's interesting. Potassium iodide; that's the stuff we want to get out, and
sodium bicarbonate. All right.
So sometimes they have a uh..
sodium iodate in the
salt for the iodine source
Ah, that would complicate things. I could still do it
I think I would just ah bake it, in an oven, at 500 degrees centigrade to ah decompose the iodate into
iodide
You know this is kind of like math you know convert
into a form that you've already solved or that you know how to solve right?
there is a lot of Sodium chloride here,
not very much, sodium-iodide.
in fact says on here that it's got 67 as that
micrograms per serving
Okay, so that's approximately 32 milligrams of iodine
For each of these cans, and considering that that is ah...
737 grams of salt; yeah the percentage is very low.
Should still be extractable though.
All right first thing we got to do is open up one of these cans.
I'm gonna pour it over into this beaker here
Okay now that that's done
I've got a bunch of sodium chloride crystals with a little bit of potassium iodide and
You know some other stuff. I'm pretty sure that the
potassium iodide is not
locked inside of the salt crystals. I'm pretty sure they just add it to it after the fact, which means..
I don't have to dissolve the entire amount I can just wash it off.
Now I could do that with water
but that would be really hard because then you just end up with a solution with a bunch of salt in it so
Let me use something that is..
Does not dissolve salt,
but will dissolve the iodide
sodium chloride, almost completely insoluble only a maybe a few milligrams will dissolve in a
liter of acetone. Iodides however, are extremely soluble in organic solvents.
So let me just
tip some in here
So I'll just stir this around make sure the acetone contacts all of the salt grains
And therefore, dissolve away, all of the iodide.
Might have to add more...
One thing I'd like to mention real quick,
is that I'm working at very low temperatures.
If you're working during the summer, and the acetone had a higher vapor pressure,
you'd want you to do this in a fume hood. Which I will be getting soon by the way
Okay, now that I'm pretty sure that all of the iodide has been dissolved. I'm gonna take the acetone and pour it
through a little vacuum filter into a 1 liter flask
This is to remove the anti-caking agent.
Okay after washing several times and using
almost filling my 1 liter flask. I think I've got most of the iodide out of here
So if you haven't already guessed the reason I'm doing this
Inside of my distillation apparatus is I'm going to distill off the acetone and reuse it.
Well here's the first batch of
ahh iodine depleted salt.
Once this dries, uhh, it should be safe to eat again
Although without the iodine, what's the point right?
Alright, it seems to be working well enough.
I am realizing this is gonna take a long time to do all six of those cans though
Maybe I'll just stop after a couple.
And that's just about it.
I transferred all of the acetone over
Hopefully all my iodine has stayed. Oh, yeah, there's a little bit of
crusty white stuff in there
As I'd expect.
Not very much, though.
I'm good.
Well, let's run this through some more salt then.
It is boiled dry
there's my
acetone.
I've just done three of these.
So now that I've got my
"hopefully," concentrated iodine
All of the acetone has been evaporated off. I'm gonna add some water
To finish dissolving, you know, to re-dissolve it.
So that I can transfer it out of the vessel
into a little beaker here
Excellent.
Let's rinse it a couple of times
So now what I've got is a stir bar mixed with some sodium iodide,
sodium chloride, because it's not completely insoluble
And of course a little bit of slightly burnt dextrose so yes a little bit sugar water probably
Okay, mixture is a little cloudy
It's probably not anything to worry about so now I'm going to add a little bit
of a silver nitrate solution
this is to
precipitate all of the
halides out of solution
as silver chloride and silver iodide
Silver iodide is a nice yellow color and you can see
a yellow a precipitate has formed.
Excellent.
Has worked. Put this into a slightly bigger vessel here
Yeah, that's definitely iodine
You can see the
silver iodide already started darken and a little bit of light that I got here
So let's uh get the iodide separated from the chloride shall we. This is a little bit of ammonium hydroxide
and this will dissolve cause the
silver chloride to become soluble, but the silver iodide
to not be soluble.
So this will dissolve
all of the chloride
Leaving just the iodide the sugar and the chlorides should all be dissolved
So let's just pour this off, and I should be left with silver iodide
It will darken over time as the light exposure,
causes it to turn into silver metal. But that shouldn't cause too much trouble for me
Now I know you all aren't gonna be satisfied until I've got this trimmed into elemental iodine
so I'm gonna wash this with some distilled water
a few times to remove excess silver and of course the other salts
the ammonia would also cause trouble so
let's get rid of it I
It will lose some iodine doing this, but you know I'll save the wash water
Now that I've got it washed pretty well. I'm gonna convert the silver iodide back into sodium iodide,
by adding a little bit of sodium hydroxide here the silver will form silver oxide
and of course
I'll end up with a little bit of
sodium iodide
So now I should have a solution of sodium iodide in water. I'm gonna decant this into a test tube.
So now I'm gonna acidify the solution with a little bit of hydrochloric acid
Okay
And now add in some hydrogen peroxide
There we go
elemental iodine
So I'll let this finish reacting. We'll go decant off the liquid, and we'll go look at the iodine in the sunlight
There it is. It's probably not super pure..
And.. I'll tell you right now our recovery wasn't great
There should have been about a hundred milligrams in that sample of salt I did
And it looks to me like I probably recovered between five and ten milligrams of iodine
But I was able to do it
Hope you enjoyed I'll see you next time
Let's take some of the silver iodide that I poured off
and let's not add the,
sodium hydroxide to it. Let's just jump straight to sulfuric acid.
In goes the acid..
I don't see anything happening there
Well it's turned back to yellow.. Very interesting