Nick Bullough wrote:
> I've googled around and turned up some information, but no real protocols
> for histology. Can the collective wisdom of histonet come up with anything?
> What I do have so far is:
> C.I. number: C.I. 30235
> preferred name: Chlorazol Black E
> I've some hints that it is used in parasitology, entomology and agriculture
> (for staining fungal hyphae in tree roots!).

I don't know about an "azo black." 

Chlorazol black E is probably not used enough. It will 
stain almost anything in shades of grey and black, often 
with pink and green bits too. Several published applications
are cited by R.W.Horobin in Chapter 11 of the new edition of
Conn's Biological Stains, including insect and plant 
applications in the early 1990s. Keep your old stock
because the dye is now quite pricey - $66.80 for 25g in
this year's Sigma catalogue.

Use a 1% solution in 70% alcohol; needs lots of magnetic
stirring, and then filter. The solution deteriorates,
with settling of insoluble black stuff, but is usable
for 6-9 months. Stain paraffin sections for 10 min
(the time doesn't make much difference), differentiate
in 95% alcohol (2 X 1 min, more or less according to
what you want to see), then complete the dehydration,
clear and cover. Thin sections (5um or less) are needed
if you want to see fine detail - as with other dark
stains.

H.G.Cannon introduced chlorazol black E in 1937 as a simple 
alternative to Heidenhain's iron-haematoxylin method 
(Nature 139:549). I can't imagine Nature publishing a paper 
nowadays with only one author and about a staining method
that's for ordinary light microscopy!
-- 
-------------------------
John A. Kiernan
Department of Anatomy and Cell Biology
The University of Western Ontario
London,   Canada   N6A 5C1
   kiernan@uwo.ca
   http://publish.uwo.ca/~jkiernan/