# Plastics compatible with OsO4?



## Joe Skulan (Mar 29, 2016)

I am trying to figure out a safe way of handling small amounts of osmium tetroxide in a vacuum line. It’s difficult to design a vacuum setup that is made entirely of glass. At minimum you need a grease to seal ground glass connections and valves. I have not had much luck getting direct information on which, if any, plastics and greases are compatible with OsO4. I have one reference stating that caps for glass bottles of OsO4 should be lined with PTFE, indicating that PTFE is non-reactive with OsO4, but then I came across an observation of PTFE coatings on stirring rods being destroyed in OsO4 dihydroxylation reactions. 

Silicone seems to be the most promising material, as silicone rubber molds are used when fixing tissue samples with OsO4. So, my questions are:

1. Can silicone grease be used with OsO4 in vacuum lines?
2. Can silicone rubber objects (O-rings, septa, stoppers, etc.) be used with OsO4? If so, what particular formulation of silicone works?

Getting information on Os compounds is difficult, even for workhorse compounds like OsO4. Beyond the fact that these compounds exist, my search for information on Os (I, II, III) iodides and (III, IV) bromides so far has turned up a few melting/decomposition temperatures and little else. I wish I still had access to an academic library. I think I’ll have to plan a trip to spend a few days in one. Hoke mentioned that in his time there was a lot of secrecy about these things, and I suspect that still is the case. But persistence will pay off.


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## g_axelsson (Mar 29, 2016)

I think that organic compounds are bad over all, corn oil is the classical way of destruction of osmium tetroxide.
https://www.emsdiasum.com/microscopy/technical/datasheet/19100.aspx

Osmium tetroxide is a really nasty chemical, one of the worst ones, not far below some radioactive substances in my opinion.
http://www.chemistry.ucla.edu/sites/default/files/safety/sop/SOP_Osmium_Tetroxide.pdf
A 2 ml spill is called a large spill and warrants a call to 911! :shock: 

With that said I would guess that silicon would hold up to osmium tetroxide, but anything that have come in contact with OsO4 should be treated as contaminated so keep down the size of any apparatus.
Also consider that osmium tetroxide could accumulate in some spots and give you a nasty surprise in the end. Any non-reactive surface could be covered in a thin invisible film of osmium tetroxide. Ordinary plastics on the other hand have the advantage that any contaminated surface turns black.

Göran


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## Joe Skulan (Mar 29, 2016)

I know (though OsO4 is candy compared to BrF5), but it is useful as a precursor to other things, and it can be handled safely. In the process I'm thinking about at any given time there would only be a small amount (< 0.5 mg), as it traveled from its point of production where it would be reacted. I might even immerse that part of the line in a tank of corn oil. But unless I want to make the whole thing out of a single piece of glass, which would be extremely impractical, I need good seals, which means I need a vacuum grease that will not react with OsO4, or through which OsO4 cannot diffuse more easily than normal atmospheric gasses.


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## Lou (Mar 29, 2016)

First, download Georg Brauer's compilation from science madness library. Then, read the book (it has a section on Os). Then practice with Re2O7. 

When I have to distill Os or Ru, I grease the joints with 98% sulfuric acid. The traps (past condensation flask) are EtOH/KOH. An easy way to determine if there's a leak (since this must be done in a hood) is to take a piece of kimwipe and wet with a little ethanol. Hold it by the joints and if it goes brown/black, that is OsO2 and you have a leak (of money). 

You can in fact use Krytox 240 AC grease for these.

As for storage, best is in a pyrex round bottom flask with a stopcock.

OsO4 smells a lot like ozone to me, so if it smells like O3, clear it! It irreversibly plates mucous membranes with OsO2, so inhalation of it causes death by asphyxiation.

Happy trails!


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## Joe Skulan (Mar 29, 2016)

Thanks for the tips. Yes, it will all be in a chamber in a hood, with a KOH trap. All I'm doing now is planning, and won't do anything at all if I can't do it right.


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