> "Histology, Metro Lab" wrote:
> My question is how to order methanamine, we have a chemical,
> hexamethylene tetramine, that we are using as methanamine.

Hexamethylene tetramine (often run together as one 
word) is the same as methenamine. Another name for 
the same stuff is hexamine. It is the stable solid 
(but water-soluble) product of the rapid chemical
reaction of ammonia with formaldehyde. The reaction
of formaldehyde with ammonia is a reversible one. 
In an aqueous medium the equilibrium is heavily 
weighted in favour of the addition compound, so the 
concentrations of formaldehyde and ammonia are low. 

In methenamine-silver methods, hexamethylene
tetramine serves two purposes: 1. to sequester 
silver ions (lowering their concentration) and 
2. to provide a low-power reducing agent that 
can reduce silver ions to silver atoms at
certain catalytic sites in a section. 

In practice the catalytic sites are aldehyde 
groups generated by oxidizing certain large
carbohydrate molecules. Methenamine-silver
does much the same job as Schiff's reagent,
but it provides an additional element of 
amplification. 

Hexamethylenetetramine has many industrial uses,
so it is a cheap chemical - the sort of stuff you
buy in kilograms when you need grams. It also has
a therapeutic application in the treatment of
urinary tract infections. After oral ingestion and
absorption it is excreted in the urine, and it is
bad news for bad bacteria in the bladder. The 
antibacterial action is probably due at least in 
part to the release of small amounts of 
formaldehyde.

To summarize: Buy hexamethylenetetramine for
use in sny "methenamine-silver' or
"hexamine-silver" stsining technique. 
Avoid high prices. This is a cheap chemical.
-- 
-------------------------
John A. Kiernan
Department of Anatomy and Cell Biology
The University of Western Ontario
London,   Canada   N6A 5C1
   kiernan@uwo.ca
   http://publish.uwo.ca/~jkiernan/