[Histonet] Silly Question? - Need help quickly!

Merced Leiker leiker <@t> buffalo.edu
Thu Dec 11 12:18:43 CST 2008

So...is a polymer of paraformaldehyde considered "depolymerized" if it 
remains somewhere between 1-50 molecules long once it's been  dissolved in 
solution, however it's dissolved? (the dissolving being a separate topic of 
debate on Histonet).  Does it matter for tissue fixation purposes if there 
are formaldehyde chain lengths of 50 molecules present in solution - not 
long enough to precipitate out, but perhaps long enough to affect its 
penetration and fixing of tissues?  Any ideas?


--On Thursday, December 11, 2008 9:58 AM -0800 Rene J Buesa 
<rjbuesa <@t> yahoo.com> wrote:

> Joyce:
> Methanal, which is the chemical name of formaldehyde, polymerizes. If it
> forms a polymer of at least 50 molecules or more, it gets solid =
> para-formaldehyde. Formalin (a trade name as formol is also another trade
> name)is the 37-50% aqueous solution of formaldehyde (with some
> additiveses to prevent polymerization). You can prepare BNF using the
> formalin solution or dissolving the amount of solid para-formaldehydede
> to get to the concentrationon you desire. The chemical in both solutions
> is the same = methanal or formaldehyde.René J.
> --- On Thu, 12/11/08, Weems, Joyce <JWeems <@t> sjha.org> wrote:
> From: Weems, Joyce <JWeems <@t> sjha.org>
> Subject: RE: [Histonet] Silly Question? - Need help quickly!
> To: "Pat Flannery" <pjfnefro <@t> duke.edu>, histonet <@t> lists.utsouthwestern.edu
> Date: Thursday, December 11, 2008, 12:12 PM
> I was just going to post a question regarding paraformaldhyde myself!
> Just last week I believe I remember someone saying that paraformaldehyde
> and formalin are the same and they had put the same solution in two
> different containers for one of their researchers because they were so
> insistent to have two different solutions. Are they the same?
> Well, today I have a request to put tissue for a researcher in formalin
> and paraformaldehyde. So.... Without percentage required, do I use 10%
> NBF? Do I call somewhere and get paraformaldehyde and make 4%
> paraformaldehyde?
> I have asked the surgeon twice for the number for the lab so I can find
> out - don't have it yet. I have two fresh adrenals in the fridge. Help!!
> Thanks in advance...
> Joyce
> Joyce Weems
> Pathology Manager
> Saint Joseph's Hospital
> 5665 Peachtree Dunwoody Rd NE
> Atlanta, GA 30342
> 678-843-7376 - Phone
> 678-843-7831 - Fax
> -----Original Message-----
> From: histonet-bounces <@t> lists.utsouthwestern.edu
> [mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Pat
> Flannery
> Sent: Thursday, December 11, 2008 11:59 AM
> To: histonet <@t> lists.utsouthwestern.edu
> Subject: [Histonet] Silly Question?
> Please humor me on this if it's obvious (to everyone but me):  why do we
> use paraformaldehyde (which is so inconvenient to make up) rather than
> buffered formalin or just diluted formaldehyde itself?
> It seems that around here, some folks prefer paraformaldehyde (either 2%
> or 4%) and others use formalin, while some others stick to diluted
> formaldehyde (I see all 4 on labels for specimens submitted for
> histology).  Is it mostly a matter of personal preference or where you
> were trained (i.e. force of habit) or is there a valid reason to use
> each solution (basically the same chemical once in solution, merely
> buffered or not)?  The only answer I've gotten when I've asked is,
> "That's what we always use."
> Thanks.
> -Pat Flannery (not a "real" histologist - I just play one in the lab)
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Merced M Leiker
Research Technician II
354 BRB (pkgs) / 140 Farber Hall (letters)
School of Medicine and Biomedical Sciences
State University of New York at Buffalo
3435 Main St, Buffalo, NY 14214
Ph: (716) 829-6033
Fx: (716) 829-2725

"Without my flaws I'm really very boring."
- random internet blog commentator

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