On Mon, 30 Oct 2000, Rae Ann Staskiewicz wrote:

> When we do the PTAH, we mordant in Zenker's which we buy from Newcomer
> Supply. It does not contain mercury, instead I believe it is zinc. The
> PTAH still works wonderfully.

  Zenker's fixative is a chromium-mercury-acetic mixture that was
  indroduced in 1894, at about the same time as formaldehyde (Blum, 
  1893) and formaldehyde with zinc chloride (Fish, 1895). At that 
  time chromium trioxide, potassium dichromate and mercuric chloride 
  had all been used in fixative mixtures for 30 or more years. 

  The first published substitution of zinc salts (chloride or
  sulphate) for mercuric chloride in mixtures containing potassium 
  dichromate may be a short note by  Barszcz,CA (1976): Use of zinc
  chloride in Zenker-type fixatives. Histo-Logic 6(4), 87.

    The point I'm trying to make is that if someone is selling a 
    non-mercury liquid as "Zenker's fluid" he can expect to be 
    haunted by Zenker's ghost, and may the fibres of his rectus 
    abdominis muscle lose their striations and become swollen,   
    amorphous and darkly staining (Zenker's degeneration).

  Zinc salts and mercuric chloride do not react identically with
  proteins. otably, zinc chloride or sulphate lowers the pH much 
  more than mercuric chloride (which is largely unionized in water). 
  Zinc salts probably do not provide the same sub-microscopic 
  texture of cytoplasmic coagulation as that brought about by 
  mercuric chloride, but this probably does not matter for most 
  purposes.

 John A. Kiernan,
 Department of Anatomy & Cell Biology,
 The University of Western Ontario,
 LONDON,  Canada  N6A 5C1