Also, John said "formalin" - was the solution formalin or 37% formaldehyde  - without buffers? Would that make a difference? Joyce-----Original Message-----From: histonet-bounces@lists.utsouthwestern.edu[mailto:histonet-bounces@lists.utsouthwestern.edu]On Behalf Of Morken,Tim - LabvisionSent: Thursday, May 12, 2005 2:08 PMTo: 'John Kiernan'; Andrea GranthamCc: histonet@lists.utsouthwestern.eduSubject: RE: [Histonet] quick question about formaldehydeJohn,  you said "   Small amounts of methanol and formate ions are not goingto change the fixative properties."But after 12 years  will it really be a "small amount?" How do we know whatpercentage of the solution will have been converted? Tim Morken-----Original Message-----From: histonet-bounces@lists.utsouthwestern.edu[mailto:histonet-bounces@lists.utsouthwestern.edu] On Behalf Of John KiernanSent: Thursday, May 12, 2005 10:48 AMTo: Andrea GranthamCc: histonet@lists.utsouthwestern.eduSubject: Re: [Histonet] quick question about formaldehydeTwo things could have happened to unopenedformalin in 12 years:1. Polymerization (to paraformaldehyde). This is   evident as a white precipitate. It slightly   reduces the concentration in the liquid,   but that does not matter for fixation.   Polymerization is accelerated by low room   temperature, and it is claimed that the   process can be reversed by autoclaving(paper   in Stain Technol about 40 years ago).2. Cannizzaro's reaction, in which 2 molecules   of formaldehyde react together, producing   one molecule each of methanol and formic   acid. This happens in all formaldehyde solutions   and causes lowering of the pH. This doesn't matter    if you make a neutral buffered fixative solution.    Small amounts of methanol and formate ions are not    going to change the fixative properties.Bottom line: OK to use, but be sure to check thepH of the working fixative solution and adjust ifnecessary.-- -------------------------------John A. KiernanDepartment of Anatomy and Cell BiologyThe University of Western OntarioLondon,   Canada   N6A 5C1   kiernan[AT]uwo.ca   http://publish.uwo.ca/~jkiernan/   http://instruct.uwo.ca/anatomy/530/index.htm_______________________________Andrea Grantham wrote:> > One of the labs here is closing and they have a case of formaldehyde, > 37.5%, that they are trying to give away. They have had it in their > lab since 1993. The bottles have not been opened. Is it still good to > use? Andi > .....................................................................> : Andrea Grantham, HT(ASCP)     Dept. of Cell Biology & Anatomy     :> : Sr. Research Specialist       University of Arizona               :> : (office:  AHSC 4212)          P.O. Box 245044                     :> : (voice:  520-626-4415)        Tucson, AZ  85724-5044    USA       :> : (FAX:  520-626-2097)          (email:  algranth@u.arizona.edu)       :> :...................................................................:>            http://www.cba.arizona.edu/histology-lab.html> > _______________________________________________> Histonet mailing list> Histonet@lists.utsouthwestern.edu > http://lists.utsouthwestern.edu/mailman/listinfo/histonet_______________________________________________Histonet mailing listHistonet@lists.utsouthwestern.eduhttp://lists.utsouthwestern.edu/mailman/listinfo/histonet_______________________________________________Histonet mailing listHistonet@lists.utsouthwestern.eduhttp://lists.utsouthwestern.edu/mailman/listinfo/histonetConfidentiality Notice ** The information contained in this message may be privileged and is confidential information intended for the use of the addressee listed above. If you are neither the intended recipient nor the employee or agent responsible for delivering this message to the intended recipient, you are hereby notified that any disclosure, copying, distribution or the taking of any action in reliance on the contents of this information is strictly prohibited. If you have received this communication in error, please notify us immediately by replying to the message and deleting it from your computer.Thank you. Saint Josephs Health System, Inc.