On Tue, 1 Jun 1999, A. F. Brandwood wrote:

> One of our Pathologists has asked me if there is a method to demonstrate
> arsenic in the liver and kidney of sheep.I cannot find any methods, can
> anybody please offer any suggestions.

   This is a tough one. Pearse's histochemistry has nothing to offer.
   Arsenic compounds react with hydrogen sulphide to give insoluble
   As2S3. This is yellow, and unlikely to be visible, but could
   probably be amplified with a physical developer ("autometallography"
   or Timm's sulphide-silver method). However, this procedure
   demonstrates pretty well every metal that has an insoluble sulphide,
   so it would have no specificity for As.

   Phil Oshel's suggestion of X-ray analysis in a suitably equipped
   SEM sounds good, but it isn't classical histochemistry. There is
   a Japanese investigator, Y. Sumi, who has developed histochemical
   methods for inorganic substances based on combinations of 
   chromogenic reagents with mixtures of "masking" agents that block
   the reactivity of elements other than the one you want to stain.
   His best known methods are for Cd and Hg, but he may have done
   something for As. A MedLine search might reveal something.

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