[Histonet] FW: formalin neutralizers

[Tony Henwood]

This is what we use:
Neutralization and Disposal of Formalin Fixative

10% Formalin can be neutralised with sodium bisulfite or concentrated ammonia. The reaction with ammonia results in the formation of hexamethylenetetramine (commonly known as hexamine or methenamine). This can then be safely disposed of either as a liquid fertiliser or via the sewage system (check with your local authority).

The reaction proceeds as follows: 

6 CH2O + 4 NH3 → C6H12N4 (Hexamethylenetetramine) + 6 H2O

Procedure:

1.	Before beginning, personnel must have the following safety equipment readily available in the event of an accidental spill:  sorbent material (spill pillows, bulk sorbent) formaldehyde rated respirator. 
2.	Personnel must wear a lab coat or apron, safety goggles and neoprene gloves. 
3.	A pH meter or pH paper
4.	To 1000 ml of 10% formalin (= 4% formaldehyde) add 56 ml of strong ammonia solution (27%). This will generate 31 g of hexamine (approximately a 3% solution).
5.	Stir well.  Reaction may produce heat.  
6.	Initially, the pH of the formaldehyde solution will be about 6.  As ammonia is added and stirred, a fluffy white precipitate will result.  Addition of sufficient ammonia will raise the pH to about 8.  Because the neutralization of the formaldehyde requires less molecules of ammonia than the apparent acid-base reaction supplies hydronium ions, the pH change from acid to base is used as an indicator that an excess of ammonia has been added. 
7.	Let set overnight (12 hours).
8.	The smell of formalin is greatly reduced or replaced by a faint whiff of ammonia.
9.	Schiff's reagent is perhaps the best, most sensitive and available reagent in any lab to test for the presence of aldehydes. If the "neutralized" formalin turns purplish with the addition of Schiff's reagent, it is not totally neutralized and you will need to add more ammonia.
10.	Dispose of appropriately


Regards

Tony Henwood JP, MSc, BAppSc, GradDipSysAnalys, CT(ASC)
Laboratory Manager & Senior Scientist
Tel: 612 9845 3306
Fax: 612 9845 3318
the children's hospital at westmead 
Cnr Hawkesbury Road and Hainsworth Street, Westmead 
Locked Bag 4001, Westmead NSW 2145, AUSTRALIA 




-----Original Message-----
From: histonet-bounces <@t> lists.utsouthwestern.edu [mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Burton, Lynn
Sent: Wednesday, 25 March 2009 6:38 AM
To: histonet <@t> lists.utsouthwestern.edu
Subject: [Histonet] FW: formalin neutralizers


 
 
Lynn Burton
Lab Assoc. I
Animal Disease Lab
Galesburg, Il 61401

________________________________

From: Burton, Lynn
Sent: Tue 3/24/2009 10:31 AM
To: histonet-bouces <@t> lists.utsouthwestern.edu
Subject: formalin neutralizers


What is everyone using to neutral their formalin? Who has the best product for the price?
 
Lynn Burton
Lab Assoc. I
Animal Disease Lab
Galesburg, Il 61401 _______________________________________________
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