[Histonet] RE: Formaldehyde vs Formalin vs paraformaldehyde(lengthy)

[Ford Royer]

No, no, Joyce.  You are all confused.

A "Formal" is a bright red farm tractor.

My uncle had three of them, and he wasn't any kind of doctor at all.

~ Ford ;-)

Weems, Joyce wrote:

>And all this time I thought it was how to dress for a party. I could have blown up! 
>
>Have a good weekend everyone... j:>)
>
>-----Original Message-----
>From: histonet-bounces <@t> lists.utsouthwestern.edu
>[mailto:histonet-bounces <@t> lists.utsouthwestern.edu]On Behalf Of Bryan
>Hewlett
>Sent: Friday, February 04, 2005 2:55 PM
>To: Morken, Tim - Labvision; histonet <@t> lists.utsouthwestern.edu
>Subject: Re: [Histonet] RE: Formaldehyde vs Formalin vs
>paraformaldehyde(lengthy)
>
>
>Tim,
>
>"Formal" is quite different, it is another name for Methylal
>(dimethoxymethane) a flammable colourless, volatile liquid used as a
>solvent.
>
>Bryan
>
>----- Original Message -----
>From: "Morken, Tim - Labvision" <tpmorken <@t> labvision.com>
>To: <histonet <@t> lists.utsouthwestern.edu>
>Sent: Friday, February 04, 2005 2:33 PM
>Subject: RE: [Histonet] RE: Formaldehyde vs Formalin vs paraformaldehyde
>(lengthy)
>
>
>  
>
>>I think "Formalin" and "Formal" were trade names from a company and just
>>went into common usage.
>>
>>
>>Tim Morken
>>
>>-----Original Message-----
>>From: histonet-bounces <@t> lists.utsouthwestern.edu
>>[mailto:histonet-bounces <@t> lists.utsouthwestern.edu] On Behalf Of Bryan
>>Hewlett
>>Sent: Friday, February 04, 2005 11:24 AM
>>To: histonet <@t> lists.utsouthwestern.edu
>>Subject: [Histonet] RE: Formaldehyde vs Formalin vs paraformaldehyde
>>(lengthy)
>>
>>
>>I was hoping that John Kiernan would jump in reply to this issue with his
>>usual eloquence! However, here goes.
>>
>>Confusion in terminology has been common since Blum introduced this agent
>>    
>>
>as
>  
>
>>a fixative in 1893! It never ceases to amaze me that this should be so,
>>    
>>
>the
>  
>
>>issue has been repeatedly addressed in all major Histotechnology texts
>>    
>>
>since
>  
>
>>before the early fifties ( my student days in the UK).
>>
>>The following information is from the 10th Edition(1981) of the Condensed
>>Chemical Dictionary and the10th Edition(1983) of the Merck Index (the only
>>ones at hand).
>>
>>Formaldehyde is a gas.
>>It is readily soluble in water up to 55% and is commercially available to
>>    
>>
>us
>  
>
>>as 37%, 44% and 50% aqueous solutions which may contain up to 15%
>>    
>>
>methanol.
>  
>
>>These commercial grades are called Formalin.
>>
>>Formaldehyde solution (Merck Index)
>>The USP grade is about 37% (37-40%)  w/v formaldehyde gas in water,
>>    
>>
>usually
>  
>
>>with 10-15% methanol added to prevent polymerization. This solution is
>>considered to be full strength and is also known as Formalin 100% or
>>Formalin 40 which signifies that it contains 40 grams of formaldehyde
>>    
>>
>within
>  
>
>>100mL of the solution. It is this solution that produces most of the
>>confusion since it is referred to and thought of as 100% Formalin.
>>
>>Paraformaldehyde (Merck Index)
>>A white crystalline powder of polymerized formaldehyde, obtained by
>>concentrating formaldehyde solution. Upon solution in water
>>    
>>
>depolymerization
>  
>
>>and evolution of formaldehyde occurs. Thus an aqueous solution containing
>>    
>>
>4
>  
>
>>grams of paraformaldehyde is essentially the same as a solution of 4%
>>formaldehyde. There is NO such thing as a solution of paraformaldehyde.
>>Right John?
>>
>>The concentration of formaldehyde used for fixation has been the subject
>>    
>>
>of
>  
>
>>much confusion (see above). The concentration of formaldehyde in compound
>>fixatives varies widely - ranging from 0.5 to 15% w/v. The majority of
>>fixatives, using formaldehyde as the sole fixative agent, have a
>>concentration of formaldehyde between 2.5 and 4% w/v. The concentration of
>>formaldehyde in a fixative should be stated as the percentage by weight of
>>the gas, rather than as a percentage of the
>>formalin(sic) or paraformaldehyde(sic) used to prepare it.
>>
>>Thus:
>>"4% formaldehyde" - not 10% formalin.
>>"4% formaldehyde, from paraformaldehyde" -  not 4% paraformaldehyde. "NBF
>>means Neutral buffered formaldehyde" - (not formalin) and is 4% w/v
>>formaldehyde in phosphate buffer pH 7.0- 7.2.
>>
>>Bryan Hewlett
>>
>>Consultant Technologist
>>QMP-LS
>>
>>
>>
>>
>>
>>
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>>    
>>
>
>
>
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