Place a 1/2 liter* of Formalex (manufactured by Sasco of Albany, GA and distributed by American Biosafety from California)  in the waste flash prior to the perfusion / fixation procedure. 

After the procedure is over give the neutralized waste to Environmental Health and Safety for proper disposal of the cacodylate buffer.

When disposing of pre-collected waste, add the Formalex in the same ratio as above, agitate the solution slightly and wait ~ 1.5 hours.

* Note: We usually generate <3.5 liters of liquid waste per procedure: <2 liters of fixative and <1.5 liters KRC.  At 4 % formaldehyde (the highest we’ve used recently) this produces a 2.3% formaldehyde solution.

 The directions for neutralizing a 3.7% solution call for a 1:4 dilution or a 20% final concentration of Formalex.  At 2.3% formaldehyde a 12.4% final concentration should suffice. That equals 496 ml formalex in 4 liters total volume. The gluteraldehyde is negligible (0.5% glut. would take a 1:36 dilution). EHS supplies us with the Formalex