Recently I was trying to resolve the problem of cutting avian tissue that 
is still heavily impregnated with bouins/picric acid even though it has 
been left in 70% alcohol for several days. The only way to cut the tissue 
was to leave it on watery-ice for up to an hour. I then left the tissue in 
95%alcohol O/N which removed most of the residual bouins, making cutting 
much easier. If you look at your the 95% and absolute solutions of the 
tissue processor even after putting through small numbers of bouins fixed 
specimens there is still significant discolouration of these solutions. 
This suggests that the 70% alcohol is limited in its ability to remove 
residual bouins.
Gerard Spoelstra
School of Biomedical and Veterinary Science
Murdoch University
Western Australia

At 04:04 PM 26/07/01 -0400, you wrote:
>"Gaskill, Betty A" wrote:
>
> >  Does anyone know a minimum amount of time bouins fixed tissue should stay
> > in 70% alcohol before being processed?  A few hours?
> > Any info would be appreciated.
> > Betty
>
>I was taught to use 4 changes of 50% ethanol, 60 to 90 minutes each, to remove
>the picric acid from the tissue (relatively small pieces of rodent tissues,
>longer time might be needed for larger tissues?). Inadequate removal of
>picrates before embedding leads to long-term damage to the tissue. This can be
>a factor if sections are needed later. The artifact section of the third
>edition of the AFIP manual shows the damage.
>
>Geoff
>--
>**********************************************
>Geoff McAuliffe, Ph.D.
>Neuroscience and Cell Biology
>Robert Wood Johnson Medical School
>675 Hoes Lane, Piscataway, NJ 08854
>voice: (732)-235-4583; fax: -4029
>mcauliff@umdnj.edu