Sciencemadness Discussion Board

What to do with HgI2

woelen - 8-11-2008 at 10:20

A friend of mine has given me some HgI2. This is a very beautiful powder, with a deeply saturated orange/red color. This powder has the peculiar property that it is not wetted by water. When added to water, it floats on top of the water and when shaken, droplets of water are enclosed by the powder, and as such can float on the surface for quite some time before they break.

I am wondering if any one of you can give some good suggestions of experiments/demonstrations with this chemical. Keep in mind that it is very toxic and gives nasty waste, so only experiments on a microscale are interesting for me.

Xenoid - 8-11-2008 at 10:51

A couple of quickies from Mellors;

HgI2 exists in two forms, red and yellow. If the red form which is tetragonal, is heated above 130 oC. it changes into the yellow rhombic form. This reverts to the red form on cooling and scratching. HgI2 melts at 259 oC. to a red liquid, and a part sublimes forming yellow rhombic needles.

HgI2 reacts with excess KI solution to form potassium mercuric iodide (K2HgI4) and when this is made alkaline it is known as Nessler's solution. This is used for the detection of trace amounts of ammonia.

chloric1 - 9-11-2008 at 06:06

Yes Nesslers reagent but given the controversy surrounding iodine, I would oxidize this to liberate the iodine for later use and convert the mercury to its chloride.

You can never have to much elemental iodine!:D

Jor - 9-11-2008 at 08:24

This is probably not so effective for us here in the Netherlands. Iodine is not too expensive here in Holland (I got 250g for 20 EUR), and quite readily available. Besides I would be quite stressed when working with mercuric compounds, and just for a little iodine :P
And AFAIK woelen already has HgCl2.

I would use it to make nessler's reagent. Or just put it in a vial, and put in the 'compounds' section of your site, and show us the amazing bright color :P
I have seen it once myself, at school.
And maybe you can make them more beautiful (larger glittering crystals) by recrystillizing from hot methanol.

[Edited on 9-11-2008 by Jor]

chloric1 - 9-11-2008 at 12:49

Well after 8 years of having a monkey for a president , things are a little f^&*@ up here. I feel it is a stretch just to get the iodine. I watched a video on youtube where someone had a solution of mercuric chloride in a small beaker and a very large beaker with potassium iodide solution in it on a stir plate. The mercuric chloride was added to the iodide to make an orange tornado that disappeared until more mercury was added. Here is the video link orange tornado.
A very interesting way to appreciate the color of this deadly poison.

woelen - 9-11-2008 at 14:56

No, I will not use HgI2 to make iodine. As Jor said, iodine is not really special over here in NL and I can easily purchase this at a decent price. Fortunately we (still) do not have that meth-craze over here.

Thanks you all for the suggestion of making Nesslers reagent. I did not know that, but it sounds interesting. Just interesting to see how it reacts with ammonia in a rather surprising reaction.

I knew already about the redissolving of HgI2 in excess KI. I even have written a webpage about that some time ago:

http://woelen.homescience.net/science/chem/exps/hgi2/index.h...

But now I have pure HgI2 I am looking for more interesting experiments, possibly with the dry material.

Jor, also interesting to read about its solubility in methanol, that also is new to me.

Jor - 9-11-2008 at 15:12

If I was you, I would make pictures of heating HgI2. It sounds interesting that it changes colour, and changes back on cooling.

I see that you did the same experiment before, but with PbI2:
http://81.207.88.128/science/chem/exps/pbi2_2/index.html

Now you could fuse the HgI2 experiment in this webbpage. I wonder if it also decomposes above a certain temperature. It probably does, because Hg(II) is a stronger oxidiser than Pb(II). A problem would be the gaseous Hg released (at those high temps its probably gas but most will condense in upper test tube, just as it does in the pyrolysis of HgO)

I'm really interested what will happen, when doing the same thing as you did with PbI2. Or can you at least show us one of your high quality picitures of the material. I really want to see the intense color :P

Talking about PbI2, I always wanted to make some, but I have no cheap source of a small amount of lead (yes I can buy a 30Kg roll, but hey, I don't want that much, just 50 grams of lead. Besides, Pb waste is harder to dispose of than mercury. Mercury can just be labeled as 'thermometer waste', wich i cannot do with lead.

The crystallisation from methanol, I read that yesterday on versuchschemie. Would be cool to grow some HgI2 crystals :P

Have you recieved my previous email?

argyrium - 9-11-2008 at 16:34

Quote:
Originally posted by Xenoid
A couple of quickies from Mellors;

HgI2 exists in two forms, red and yellow. If the red form which is tetragonal, is heated above 130 oC. it changes into the yellow rhombic form. This reverts to the red form on cooling and scratching. HgI2 melts at 259 oC. to a red liquid, and a part sublimes forming yellow rhombic needles.
....


As an extension to what Xenoid wrote, something that sounds intriguing to try is found in "Chemistry: Inorganic and Organic" Bloxam, Chas. L., et al, Eighth ed. 1895.
ver

Skip down to Mercuric iodide..

[Edited on 9-11-2008 by argyrium]

HgI2004.jpg - 246kB

argyrium - 9-11-2008 at 16:37

"...red spots appear like poppies among corn,.."

Sounds beautiful

HgI2005.jpg - 271kB

woelen - 10-11-2008 at 12:56

I tried two of the experiments, mentioned above.

The first experiment I tried was dissolving some HgI2 in methanol and getting crystals of this from the methanol. This failed. The solubility of HgI2 in methanol is too low to be useful. Dissolving even a small spatula of HgI2 requires a lot of methanol and I was not willing to spend so much methanol.

The second experiment I tried was careful heating of HgI2 in a test tube. The result of this experiment is amazing. On heating, the HgI2 darkens. Its color shifts from very bright orange/red to a beautiful deep red/purple color. At a certain point though, almost at once the color changes from dark red/purple to bright yellow (like PbI2 at room temperature). At this point I stopped heating, just to assure that no appreciable amount of mercury-containing vapor is released.

On cooling down, the color remains bright yellow. After a few minutes, the material has cooled down again and still is bright yellow. I took a glass rod and crunched the yellow material under the glass rod. When this is done, then the powder changes from bright yellow to bright red/orange. It is really funny to see how simple crunching of the yellow granules makes the material orange/red again. After this, no trace of a yellow material could be observed anymore, all was red/orange again.

I hope to find the time to make a webpage about this phenomenon soon, it really is amazing.

Panache - 12-11-2008 at 18:52

This is very coincidental that HgI2 has come up as i was about to post a warning relating to it, however instead of beginning a new thread with an alarming subject i can add it here.

I use mercuric salts about every other year to form Al Amalgams. I have for the previous decade used HgI2 to form these, however last month i realized my 5g jar was empty. I use HgI2 because it is appreciably soluble in alcohol and my amalgams are only ever used to fully dehydrate alcohol but mainly because it is easier to make than HgCl2.

The other two times i have made HgI2 i simply ground Hg and iodine together and, voila, the salt. Its an excellent experiment. I only ever made 5g at a time. This time i made 10g and here is where my cautionary tale comes in. At this larger amount the heat of the reaction will vaporise the iodine and mercury in parts. I was happily grinding the two together in a mortar and pestle and i heard a fizzing, i stepped back from the open fume hood and witnessed a huge puff of red/yellow/dark smoke. I smelt something i had not smelt before and then got the fuck out of the room, unfortunately without closing the fume hood. The nitrile gloves i was wearing were completely stained red brown from the moment they wear close to the vapour. I immediately removed them. The lab is completely sealed and the running fume hood ensured the room was under negative pressure. The lab remained sealed until the following day to allow any vapours that may have been in the air to find a surface. Upon re-entering the room there was no detectable smell. The mortar and pestle had my most of the HgI2 in it and i sealed this into a container. I then proceeded to contact every surface with very dilute nitric acid which took 6hours.
i am confidant that if there was contamination of the surfaces of the lab this was now minimal. The lab is used for development and QC for food products and as such you can understand my concern is ensuring it was clean.


So if you are interested in making HgI2 the safest way is simply to combine the stoichimetric amouts off Hg and I into a sealed container and leave for several days, this allows the reaction to proceed slowly. If you choose to grind the two together use only small amounts and a mortar and pestle that has been in the freezer overnight.

i am still alive and (in) sane so hopefully i did not inhale much of the HgI2 in that smell i took in, time will tell, Mercury poisoning is like having unprotected sex in a way, you only find out later if your fucked. Its not a very nice situation to be in.

stoichiometric_steve - 14-11-2008 at 13:51

Quote:
Originally posted by Panache

i am still alive and (in) sane so hopefully i did not inhale much of the HgI2 in that smell i took in, time will tell, Mercury poisoning is like having unprotected sex in a way, you only find out later if your fucked. Its not a very nice situation to be in.


go see a specialized therapist/toxicologist. if you mainly inhaled the ionized form, it should still be possible to remove by EDTA salts!

woelen - 16-11-2008 at 10:13

Jor, as you suggested, I made pictures of HgI2, both of the orange/red form and the metastable yellow form. I added them to my gallery of compounds:



I also am writing a webpage about a few mercury compounds with marvelous colors and the added nice property that the color strongly depends on temperature. This is not limited to HgI2. More on this will follow later.

Unfortunately, it really is difficult to grasp the true brightness of the red/orange variation. For most monitors the beautiful bright color will be out of gamut. These can only represent a subset of the complete colorspace and the most bright colors do not belong to that subset. Especially LCD-monitors do not really render the beautiful color, but I hope the picture does give you an idea of the beauty of the color.

[Edited on 16-11-08 by woelen]

woelen - 16-11-2008 at 14:33

Well, I now also finished the webpage with a few beautiful experiments with mercury(II) iodide. If you like colorlful precipitates, then read the following link:

http://woelen.homescience.net/science/chem/exps/hgi2_thermoc...

Jor - 16-11-2008 at 14:45

Amazing. I love the colors! This is a very nice experiment. But I do believe you, i think the colors are most beautiful when one observes them in real life. I really want some HgI2. I might someday try to make it, since I have some mercuric oxide, wich is very pure (Merck). Shame it is so toxic, could have been a great dye :P

Panache - 11-12-2008 at 14:30

nice job on the webpage woelen. I assume my reddish HgI2 is just a mix of the two and i will go see a toxicologist tomorrow if that is true steve thanks for the advice.

edit, okay apparently the inorganic mercury salts are not too bad, so even if i had inhaled quite an amount in that one breath much of it would have been exhaled and what remained would be well below threshold limits, same goes for any mercury vapour in the air at the time, apparently clears in about six months, some remains in the fatty tissue and bone. EDTA is no longer used as treatment as it is often more dangerous than the metal your trying to remove, he didn't elaborate on this but apparently it has a very narrow therapeutic range.
if i had inhaled an organic mercuric compound i would be dead.
I can have a 24 urine cycle test done for environmental mercury assessment where i imagine they look for peaks around the time you leave work. Interestingly this test is free under Australian medicare.

[Edited on 11-12-2008 by Panache]

Jor - 11-12-2008 at 14:53

Yes I would see a toxicolgist. It's auite easy to remove mercury form the system by chelation therapy. I have read medical report where people had ingested 0,1g and more of mercuric salts, and they had very severe kidney failure + convulsions and other things, but they all recovered fully after a few months. So your non-lethal, probably low dose should be no problem I think to remove.



[Edited on 11-12-2008 by Jor]