Yes, you're correct but, I'm not sure if I will be able to determine 
stability by visualization alone; because my 4% doesn't get cloudy after 2 
weeks I've just been advised that it converts to formalin after that period 
of time. It is a pain to go into solution but thankfully the protocol I use 
recommends heating it until it reaches 65C then adding 3.6 ml of 1N NaOH to 
help dissolve the PFA. After cooling I Q.S. and dilute to 4% with 
Sorensen's Buffer. Will most definitely let you know if I get it figured out.

>X-Sender: gcallis@gemini.msu.montana.edu
>X-Mailer: QUALCOMM Windows Eudora Light Version 3.0.6 (32)
>Date: Thu, 25 Mar 2004 14:28:37 -0700
>To: "Atoska S. Gentry" 
>From: Gayle Callis 
>Subject: Re: [Histonet] Fwd: Shelf life of 20% PFA/ 0.1M PB
>
>Sounds like an experiment about to happen!  Can you get powder into
>solution at 20% concentration, a solubility consideration?
>
>I make 4% weeks (usually 500 mls) in advance per than answer I gave, doing
>it a day ahead is sometimes a bother - but it is a gamble to see if it
>stays viable.  My EM tech made up 4% PFA in a Sorenson phosphate buffer and
>he taught me the cloudy solution trick.  He kept his for weeks also, and
>you know how picky EM is -----. Interesting that I can make it up, split
>the batch I made, send one batch to a lab and keep other in my lab.  Theirs
>goes bad in a couple of weeks (lots of whining and long faces!) and mine
>stays good for months.  One gal using it is sloppy and probably the reason
>theirs always goes bad! Consequently, I don't volunteer to make it up for
>them too often.
>
>If you find out shelf life on 20%, let me know. Have fun -
>
>Gayle

Atoska S. Gentry B.S., HT(ASCP)
Research Assistant III
Scott-Ritchey Research Center
College of Veterinary Medicine
Auburn University, AL  36849
Phone# (334)844-5579  Fax# (334)844-5850 


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