We normally dissolve 4 gms paraformadehyde powder in 20 ml buffer with a
few drops of NaOH and heat till around 75-80C. Should only take 4-5 minutes
at most.Adjust pH to 7.3 and then make up volume. recheck pH.
usually no problems with this.
Barry

At 04:33 PM 05/23/2000 -0500, you wrote:
>dear all
>
>A 4% paraform./PBS prep has gotten out of hand.  The paraformalin will not
>go into solution.  The pH is at least 10 (by ph paper).  Temp. is 65
>deg. C.
>
>I decided to use NaOH pellets this time.  I don't know why.  Normally, I
>use 10 N NaOH.  Never have I seen this problem.
>
>Any ideas?
>
>Does anyone know at what pH paraformalin goes into solution at between 60
>and 70 deg. C?
>
>As always, thanks for the help.
>
>John Carroll Dennis
>Anatomy, Physiology, and Pharmacology
>109 Greene Hall
>Auburn University, AL  36849
>
>
>
>