[Histonet] Re: Mordant for PTAH

[RSRICHMOND <@t> aol.com]

Charlene Henry HT (ASCP), QIHC at St. Jude Children's Research Hospital 
[Memphis, Tennessee] asks:
>>We are trying to rid the lab of all mercury products and I was wondering 
what everyone is using as a mordant for the PTAH. We are currently using 4% 
mercuric chloride and I would like to replace it with another mordant.<< and Rene 
J Buesa replies>>Try using 5% potassium dichromate at 60ºC for 30 minutes. It 
has worked for me.<<

But then you have to dispose of chromium, which is as difficult as mercury to 
get hauled away, I think.

But what does anyone use phosphotungstic acid hematoxylin (PTAH) for nowadays 
anyway? Forty years ago it was of some use for staining muscle striations (in 
suspected rhabdomyosarcomas) and astrocytes - if the tissue had been fixed in 
Zenker/Helly (mercury, chromium, and formaldehyde). I recall it being said 
that the chief virtue of PTAH was that it took overnight to do the stain, and 
that gave you time enough to try to identify an unusual tumor. (It also took 
three months to make PTAH - you didn't add an oxidant, just put it on the back 
porch like sun tea.)

According to Giuseppe Verdi or his librettist, Aida praised it to the skies 
("Omnipotente Ptah" - sorry about that), but I think PTAH's fortunes have been 
in decline ever since.

Bob Richmond
Knoxville TN and Gastonia NC