RE: "Disposal" of Osmium Tetroxide "Waste"

From:Jim at ProSciTech <>

As always, John Kiernan's contribution is well researched and presented. The 
method for recycling Osmium tetroxide is feasible and has been used by some 
people. I am in a good position to know that very few electron microscopists 
practice this recycling. Maybe they are worried about the purity of the 
resulting material and certainly the concentration of prepared OsO4 is unknown. 
I should also ad that as a supplier I am surprisingly equivocal: I like people 
to recycle and minimize the use of toxic materials (with luck they'll purchase 
with saved funds other goods from us).

The reality is that few people recycle OsO4, so how to dispose of the waste?
Because OsO4 is used in labs in small quantities and because it is readily is 
reduced to fairly harmless material, I see no direct reason why not to dump 
small quantities down the drain with plenty of water. Maybe one should mix the 
OsO4 with a little full -cream milk powder to completely deactivate the O4. I 
prefer the milk powder over oil because its no so messy; in fact oil in the 
drain may be the greater evil. I see no reason to involve charcoal, which is 
another carcinogen in the process.
Incidentally, we ship OsOr vials packed in some full-cream powdered milk, 
because if there ever was a cracked vial the fumes would be deactivated and it 
also gives receiving lab a supply of powdered milk to dump over any spillage.

I wrote "no direct reason why not to . . . ", because in many places there are 
legal reasons, which compel to take a certain course of action regardless. 
Gayle Callis made that point well. Though I disagree with the term "heavy 
metal" since it has been misused as a slur. Some of the heaviest metals, 
especially by weight, but also by position in the periodic table are among the 
least harmful and some of the lightest metals are pretty toxic. Metallic Os is 
rather inert.

Dangerous Goods legislation and MSDS requirements are fairly recent 
developments. They were certainly needed, but they are still in their infancy. 
I expect that in another ten years the rules will have changed. In terms of 
shipping and storage, I hope that the requirements will be more related to 
quantities involved and safe packaging and less on paper documentation. Packing 
OsO4 with milk powder is clever, looking for very expensive paper documentation 
when a plane falls out of the sky (DG go on passenger planes) is stupid; the O4 
will rise to heaven before any passenger's soul might.

Similarly, environmentally friendly disposal cannot possibly involve 
accumulating large quantities of a substance and thereby creating a hazardous 
situation. Subsequently the squandering of considerable (environmental) 
resources is needed to dispose of something like OsO4 (or Uranyl Acetate), 
which is used in tiny quantities in the lab.
Jim Darley
ProSciTech                 Microscopy PLUS
PO Box 111, Thuringowa  QLD  4817  Australia
Ph +61 7 4774 0370  Fax:+61 7 4789 2313
Great microscopy catalogue, 500 Links, MSDS, User Notes
ABN: 99 724 136 560            

On Monday, November 27, 2000 3:22 PM, J. A. Kiernan 
[] wrote:
> On Thu, 23 Nov 2000, stephen asquith wrote:
> > disposal of this wonderful material but it still ...
> > ... containers full of osmium in alcohol or corn oil ...
> > ... what should be done with it then?
> Osmium tetroxide is indeed wonderful stuff. Os is a rare
> element, so disposal of used solutions should consist of
> recycling, not dumping, even though osmium compounds are
> not considered environmentally hazardous (Smith et al., 1978
> Trace Metal in the Environment, vol 4. Ann Arbor Science
> Publishers). The colourless soluble toxic tetroxide is rapidly
> reduced by almost any kind of dirt to a black, insoluble dioxide,
> usually in a colloidal form that's readily dispersed by moving
> water if it isn't firmly stuck to the solid organic matter that
> brought about the reduction.
> If OsO4 slops are collected in alcohol, the osmium (now in
> the form of crude, harmless, insoluble osmium dioxide) can
> be reoxidized, purified, re-reduced to pure OsO2 and stored.
> OsO2 is easily re-oxidized to give a buffered solution of
> osmium tetroxide (2% or less). See J Microsc 113:77-82
> (1978); the procedure does involve certain hazards, so
> it must be done carefully.
> Recovered OsO4 can also be used to make osmeth, which is
> a beautiful golden crystalline solid that contains osmium
> tetroxide complexed with methenamine (= hexamethylene tetramine
> or hexamine (Hanker et al., 1976 Histochemistry 49:263-291).
> It costs next to nothing to make your own osmeth from
> recycled OsO4, but osmeth is very expensive to buy. Osmeth
> does not emit osmic fumes. When it is dissolved (in DMF
> followed by dilution in an aqueous buffer) it becomes a
> dilute (0.25%) working osmium tetroxide solution. I can vouch
> for the excellence of home-made osmeth for post-osmication (for
> EM). It may also be OK as a primary fixative or for LM staining,
> but I haven't encountered (personally, by anecdote or in the
> literature) any use of osmeth other than for postosmication.
> Perhaps someone reading this message will put me right on this.
> Osmium tetroxide collected into vegetable oil could not be
> recycled by the simple method cited above, and the recovery
> methods used by chemists (which use apparatus etc not found
> in histology labs) would be made more difficult by the presence
> of the oil.
>  John A. Kiernan,
>  Department of Anatomy & Cell Biology,
>  The University of Western Ontario,
>  LONDON,  Canada  N6A 5C1

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