On Wed, 11 Jul 2001 RSRICHMOND@aol.com wrote:
> Robert Embree asks about fixatives containing barium chloride.
> 
> In 1992 Surgipath Medical Industries was marketing a fixative ...
> ... that contained "barium chloride and a very low percentage 
> of formalin. The barium chloride acts in a manner similar to 
> zinc and mercury...."
> 
> No references were given to support this statement ...

It's not easy to see how barium chloride could work as a
fixative. Ba ions don't coagulate or cross-link proteins,
and they don't combine in any histochemically useful way
with sulphated carbohydrates (see Pearse's Histochemistry).

The acute toxicity of soluble barium salts compares
unfavourably with both zinc and formaldehyde. According to
the 1998 edn of the Merck Index, the lethal doses for 
mice/rats are as follows:

BaCl2 injected      19 mg/kg
ZnCl2 injected   60-90 mg/kg

In the same book:

Formaldehyde orally       800 mg/kg
Potassium cyanide orally  10 mg/kg
 (That's 0.7 grams for a 70 kg man or woman, but 
  according to Poulson's "Toxicology" half that
  amount can be fatal to a human being.)

By extrapolation to a 70 kg human, 1.4 grams of barium
chloride could be fatal. A human lethal dose of mercuric 
chloride, according to Merck, is 1 to 2 grams. BaCl2
and HgCl2 are almost in the same league as KCN for
acute toxicity. (Barium sulphate, used as an X-ray 
tracer for the GI tract, is harmless because it's 
insoluble in water, acids and alkalis.)

Zinc chloride is decidedly less toxic than HgCl2
or BaCl2. Formaldehyde is considerably less toxic 
than any of these metal salts, and cannot therefore 
be recommended to the student murderer.
----------------------------------------
John A. Kiernan
Department of Anatomy & Cell Biology
The University of Western Ontario
London,  Canada   N6