Re: paraformaldehyde

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From:"R.Wadley" <> (by way of histonet)
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	Dear Gayle,

	30 minutes to dissolve paraformaldehyde?  You must be making up large
batches.  I used to have my paraformaldehyde weighed out, warmed,
dissolved, cooled, mixed with buffer and/or glut. and in with my specimen
in that time.  (I only made 50 - 100 ml at a time.)

	Do you add a drop of 1N NaOH per 10 ml of distilled water?

	By making the solution slightly alkaline the paraformaldehyde dissolves
much more quickly.  In the unlikely event the the pH is a little low after
the addition of buffer a drop or 2 of 1N HCl soon sets it right.  Everybody
checks the pH of their final solutions don't they?

	I never keep a fresh solution of paraformaldehyde for more than a
week at
4C, but I am EM biased.


	Rob W.

At 12:12 12/13/1999 -0700, you wrote:
>We store 4% paraformaldehyde, made up in PBS at 4C for long periods
>of time, two months or so, without problems.  If any precipitate appears
>it is tossed, and fresh is made up, carefully, using heat and stirring.
>We never heat over 60C, and it usually goes into solution at 56C within
>30 min.  Our EM facitlity warned that overheating PFA when making it up,
>can ruin the molecule, so care is taken to control that temp.
>For 2% we just dilute it with PBS.
>Gayle Callis

R. Wadley, B.App.Sc. M.L.S, Grad.Dip.Sc.MM
Laboratory Manager
Cellular Analysis Facility
School of Microbiology & Immunology
UNSW, New South Wales, Australia, 2052
Ph (BH) 	+61 (2) 9385 3517
Ph (AH)	+61 (2) 9555 1239
Fax 	+61 (2) 9385 1591

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