Re: disposal of formalin
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From: | "J. A. Kiernan" <jkiernan@julian.uwo.ca> (by way of histonet) |
To: | histonet@histosearch.com |
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On Mon, 20 Dec 1999, Linda Banks wrote:
> I am reviewing our procedures for the disposal of formalin, xylol and
> alcohols. Can others tell me how they are dealing with these chemicals and
> perhaps give me some references. Thanks!
> lbanlb@crncare.org
Here is a repeat of a message I sent to HistoNet about a year
ago, replying to a related question. It relates only to formalin,
and a one-line summary would be: Neutralize it with ammonia.
There is a reference to a book about formaldehyde.
Neutralization of formalin with ammonia
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
6CH2O + 4NH3 = C6H12N4 + 6H2O
6 * 30.03 4 * 17.03
= 180.18 = 68.12 140.19 grams
180 g CH2O are contained in 180/0.04
= 4500 ml of 4% (=0.04g/ml) solution (10% formalin)
68 g NH3 are conmtained in 68/0.27
= 252 ml of 27% (=0.27g/ml) solution (strong ammonia)
Therefore 1000 ml of 10% formalin (= 4% formaldehyde) reacts
with 56 ml of strong ammonia solution, generating 31 g of
hexamine (in an approximately 3% solution).
The MSDS for hexamine has all the usual dire warnings,
relating to the solid. Various LD50s range from 250 to 9500 mg/kg.
The sheet for hexamine mandelate (the salt used therapeutically
as a urinary antiseptic) contains much less information, and
doesn't have nearly so much in it. Hexamine and its salts
are slowly hydrolysed, releasing formaldehyde, and this
reaction, which is speeded up by acids, is probably the basis
of the antiseptic properties.
The proper name for hexamine is hexamethylenetetramine, and it's
also commonly called methenamine. The Merck Index lists many
other synonyms. For more information see Walker,JF (1964)
Formaldehyde. 3rd ed. New York: Reinhold and London: Chapman & Hall.
What I do is add about 50 ml of strong ammonia to a container
with a specimen in a litre or so of formalin fixative, but the
lid back on, give the pot a swirl, and wait for half an hour or
so (the reaction is much faster, so the wait probably isn't
really needed.) The smell of formalin is greatly reduced or
replaced by a faint whiff of ammonia.
John A. Kiernan,
Department of Anatomy & Cell Biology,
The University of Western Ontario,
LONDON, Canada N6A 5C1
E-mail: kiernan@uwo.ca
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