On Thu, 7 Oct 1999 marilyn.johnson@agric.gov.ab.ca wrote:

> Does anyone know if there is an expiry date for Bouin's solution?

   Aqueous Bouin can be kept for ever - well at least 5 or 6 years
   anyway. This is the picric-formalin-acetic fixative that most 
   people call Bouin's fluid (though he did invent more than one).

   Alcoholic Bouin and similar mixtures do change with time
   (months) and for some purposes the fixation is said to be
   better with an aged solution. Its composition is known, and
   you can make artificially aged alcoholic Bouin directly.
   I can provide the details and reference if you're interested.

   Chuck Churukian's "Manual of the Special Stains Laboratory"
   (Rochester, NY, 1997) has a big table of shelf lives. I don't
   have my copy to hand right now, but would guess that he says
   6 months. Many of the times in his table seem far too short;
   there are even shelf lives for solutions that would last for
   centuries. 

   You need to know of the potential explosive hazard
   of dry picric acid. If there's some dry yellow stuff encrusted
   round the stopper or cap of the bottle, run it under the tap
   to make it wet. Picric acid explodes when its temperature
   gets above 300C. This seems unlikely from the friction of
   undoing a tight stopper and is, of course, impossible in the
   presence of liquid water. The stock jar of picric acid must
   be inspected from time to time, and should always have a
   generous layer of water above the powder. 

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