John:
I expect that you are asking about formaldehyde applications in histology and 
you will, no doubt receive applicable replies from this excellent forum.

As an aside and because things are always more complicated than it first 
appears, here is some peripheral information:
Because of the effects of formalin contaminants that fixative was shunned as 
unsuitable for fixation on a subcellular level - EM. Purified glutaraldehyde 
was the organic fixative of choice since its introduction by Sabatini in the 
60th.
Very pure formaldehyde is actually an excellent fixative for fine structure 
(perhaps the best), but it must be prepared "on the day" from paraformaldehyde 
in a somewhat elaborate procedure.
This changed a couple of years ago when highly purified, 16% formalin became 
available. This is supplied in 10ml vials, sealed under nitrogen and is stable 
at room temperature for at least two years.
Clearly, this very pure formalin is too expensive and possible would not result 
in better fixation on the light microscope level, but I hope that you find this 
interesting.
I should declare that PST - and other suppliers to EM labs - supply pure 
formaldehyde.
Cheers
Jim Darley
ProSciTech                 Microscopy PLUS
PO Box 111, Thuringowa  QLD  4817  Australia
Ph +61 7 4774 0370  Fax:+61 7 4789 2313  service@proscitech.com.au
Great microscopy catalogue, 500 Links, MSDS, User Notes
                      www.proscitech.com.au

On Wednesday, August 04, 1999 4:51 AM, LOVE, JOHN E. (JSC-SD) 
[SMTP:john.e.love1@jsc.nasa.gov] wrote:
> I understand that the shelf life of formaldehyde solutions is affected by a
> variety of reactions including oxidation, methanol formation,
> polymerization, and condensation.  I am interested in finding out about the
> shelf life of buffered 10% formalin (4% formaldehyde) solutions stored at 4
> degrees C.
> Thank you for your help.
>                                     John
>
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