Sublimatus - 10-7-2012 at 09:46
Just today I was cleaning out a room that used to be a scanning electron microscopy lab and came across an old glass reagent bottle with a masking
tape label reading only "Osmium". The botanist who now works in that room (identifying mosquitoes, actually) suggested that it was osmium tetroxide
stored under water, claiming it was somehow used for the microscopy.
The bottle itself contains a clear liquid and a glassy brown substance sitting at the bottom of the container. Being the only chemist in the lab,
it's sort of fallen on me to find out just what's in the bottle so we can take care of it properly.
Does anyone know of a simple test or reagent that would confirm the identity of this material? The only things I know about osmium tetroxide are its
uses in organic chemistry, along with the fact that it's acutely toxic and no good for your eyes.
Edit: Now that I'm reading wikipedia, I wonder if it's osmeth. I can't seem to find a picture of it to confirm.
[Edited on 7/10/2012 by Sublimatus]
Mixell - 10-7-2012 at 09:54
Check the melting point, it should be around 40C.
Fleaker - 10-7-2012 at 19:43
Don't check the melting point. It's a deadly poison that'll metallize your lungs (let alone eyes) and kill you dead if you remove it from the water.
Add alcoholic KOH to it to make it safe; that's what we distil it into. It may be OsO2 already if it's a black powder. The real deal is clear and
yellow. You don't want to smell it as it makes a deposit that won't go away.
woelen - 10-7-2012 at 22:29
The wikipedia page has a picture of OsO4. it is a clear glass-like material with a pale yellow color. If it becomes impure, then it turns black, due
to formation of fine OsO2 particles, or even formation of metallic Os if the contaminating agent is a strong enough reductor.
As the others stated already, the material is very toxic and should not be handled in open air. It must be kept in aqueous solution and the solid must
be kept under water.
Sublimatus - 11-7-2012 at 04:03
Yes, I'm aware of the dangers of this material and had no intention of taking a melting point. 
The material under the liquid is a glassy brown solid. At first glance I actually mistook it for a broken amber glass ampule because the color is so
similar.
One page I read suggested that it was possible to test for OsO<sub>4</sub> vapors by holding a strip of filter paper that has been dipped
in a polyunsaturated fat, such as corn oil, over the open bottle. The paper/oil should go black with the formation of lower osmium compounds.
Mixell - 11-7-2012 at 04:19
I think that if he has an access to a lab, then testing the OsO4 melting point will not be as lethal as you describe it to be.
Sure it is very toxic, sure it is volatile, but I think with proper precautions it can be handled without experiencing any health issues.
Paddywhacker - 11-7-2012 at 04:46
Not osmeth. That is orange coloured.
If it is osmium tetroxide then you will notice a garlicky smell, even if it is under water, when you open the bottle.
Yes it is toxic. Supposedly, it will blind you by depositing osmium on your eyeballs. But how much exposure would it take to do that?
Heaps. Just don't hang around if you smell it. Don't wait and habituate to the smell and then not be aware of it.
Mixell - 11-7-2012 at 06:27
OsO4 is highly poisonous, even at low exposure levels, and must be handled with appropriate precautions. In particular, inhalation at concentrations
well below those at which a smell can be perceived can lead to pulmonary edema, and subsequent death. Noticeable symptoms can take hours to appear
after exposure.
http://en.wikipedia.org/wiki/Osmium_tetroxide#Safety_conside...