Re: zinc formalin (making of)

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From:"J. A. Kiernan" <>
To:"Marshall, Sharon," <>
Content-Type:TEXT/PLAIN; charset=US-ASCII

On Mon, 10 Apr 2000, Marshall, Sharon, wrote:

> I am interested in the method for making zinc formalin.  I have seen 
> a method in the histology archives but they give more then one 
> version and I was wondering which one is most frequently used for 
> immunocytochemistry. 

  It is difficult to know which one is most frequently used, or
  if the different mixtures have different effects on antigens.
  If you want to be traditional you can use Fish's fixative. This
  was introduced by Pierre A. Fish in 1895 (Trans. Amer. Microsc.
  Soc. 17: 319-330) only a couple of years after the introduction
  of formaldehyde as a fixative. He immersed human brains in it for
  7 to 10 days, and recommended injecting cavities and vessels if
  possible. Fish knew what he was about, and his paper is worth 

  Fish's fixative.
     Water                  2000 ml
     Formalin                 50 ml
     Sodium chloride         100 g
     Zinc chloride            15 g

  This contains less formaldehyde and more zinc than you'll
  find in recipes for contemporary fixatives of this kind. 
  Formaldehyde-zinc mixtures were largely forgotten for nearly a
  century, and then revived. Most published mixtures contain 3.7 to
  4% formaldehyde (=10% formalin), about the same amount of NaCl as
  Fish's, and zinc chloride (ZnCl2; 1.6g/L), or zinc sulphate 
  (ZnSO4; 3.6 g/L) or zinc salicylate (.3H2O; 5 g/L). The chloride 
  makes a more strongly acidic solution than the sulphate. Zinc 
  salicylate hardly changes the pH. Mugnaini & Dahl (1983;
  J Histochem Cytochem 31:1435-1438) recommendeded adjusting
  the pH to either 4 or 6.5 and using the solution that gave
  the better results. Zinc-formaldehyde fixatives have been
  more recently reviewed by R. Dapson (1993) in Biotechnic
  & Histochem. 68: 75-82, who also discusses their mechanism
  of action.

  Several companies sell ready-made zinc-formalin solutions,
  some of them without disclosure of the exact composition.
  Zinc chloride has also been used as an alternative to
  mercuric chloride in mixtures otherwise equivalent to
  Zenker, B-5 etc (e.g. C.A.Barscz 1976. Histo-Logic 6[4]:87).
  Zinc doesn't work the same way as mercuric chloride though,
  and there's a need for a double-blind trial to find out
  if this substitution really works.

 John A. Kiernan,
 Department of Anatomy & Cell Biology,
 The University of Western Ontario,
 LONDON,  Canada  N6A 5C1
   Phone: (519) 661-2111
   FAX (Department): (519) 661-3936


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