[Histonet] Movat's Pentachrome question

[John A. Kiernan]

Answers below begin with ****
    John Kiernan
    London, Canada.
-------------------------
"Monfils, Paul" wrote:
> 
> Does anyone do Movat's Pentachrome stain?  I have a researcher who wants to
> do it.  My question involves the "alkaline alcohol" the procedure calls for.
> The protocol says to add ammonium hydroxide drop by drop to 95% ethanol
> until the pH reaches 8.0 or higher.
> 
> Question 1, a theoretical one - How can you accurately measure pH in a
> nearly water-free solution?  Presumably an ionic compound would not ionize
> very well in such a solution?
**** You can't! There is a quantity called pH*
(pee-aitch-star)
that is can be calculated from a pH meter reading taken from
a
non-aqueous solution. (see Perrin & Dempsey's book on
Buffers).
It's complicated stuff, and I don't claim to understand it.
The
book says you can get pH* standard buffers to calibrate a
glass
electrode pH meter for solvents that contain "at least a few 
percent" of water.
> 
> Question 2, a practical one - When I put the pH probe into 95% ethanol, the
> meter already reads higher than 9.0, even without adding any ammonium
> hydroxide. Is this your experience?
**** Never tried!
>