On Fri, 23 Jul 1999, R.Wadley wrote:

> When I last used uranyl & lead I would still combine the 2, but I would
> periodically add an excess of NaOH conc solution.  This precipitates out
> all the heavy metal & leaves you with a clear supernatant.  From time to
> time the supernatant can be poured off (down the sink, plenty of running
> water) & your container gradually fills with the precipitate.  This allows
> use of a smaller (0.5 litre/1pint) container & fewer calls to the guy
> hauling the chemical waste away.  

   This is a classic answer. Straightforward Chemistry 101, and it
   will save great quantities of valuable money because it reduces
   the volume of sludge that has to be treated as "hazardous." 

> The other alternative is to extract the uranyl nitrate & re-use it.  This
> is also true for osmium tetroxide & a whole lot of other nasties.

   For uranium it probably isn't financially viable. For silver you
   should collect precipitated silver chloride and sell the sludge to
   a reclamation company. Osmium recycling is easy but the method is
   likely to draw repercussions from the Lab Safety Police. This is
   unfortunate because Os is a rare element. It is easy and quite
   safe to recycle gold chloride in the lab. Here's where to find
   detailed instructions for reclaiming gold and osmium.

    Kiernan, J. A. 1977. Recycling procedure for gold chloride used in
      neurohistology. Stain Technology 52, 245-248.
    Kiernan, J. A. 1978. Recovery of osmium tetroxide from used fixative
      solutions. Journal of Microscopy 113, 77-82.

   I haven't bought any new HAuCl4 or OsO4 for nearly 20 years. Recycled
   materials from my lab and those of my colleagues have been more than
   adequate to meet our needs. Recycled osmium can easily be incorporated
   into osmeth, a beautiful gold-coloured complex of OsO4 with
   hexamethylene tetramine. Osmeth doesn't give off noxious fumes but it's
   just as good as OsO4 for post-osmicating bits of tissue previously
   fixed in glutaraldehyde and/or formaldehyde. You can buy osmeth from
   Polysciences (if you are a millionaire), and perhaps also from other
   companies. It is very easy to make your own by following the
   published instructions (Hanker, Romanowicz & Padykula 1976.
   Histochemistry 49: 263-291).

 John A. Kiernan,
 Department of Anatomy & Cell Biology,
 The University of Western Ontario,
 LONDON,  Canada  N6A 5C1