pX is used only as a placeholder...
It indcates only that we could be talking about any halogen,
Regardless of the halide ratio, the absolute Ag+ in solution is the item of concern. With that in mind, pAg or vAg then becomes the measure of choice. With mixed halides or between Cl/Br/I and mixtures thereof the pX can be just about anything, but equimolar Br and I for example alone will give nearly the same pX or vX, but the vAg or pAg may be different by a huge amount. Therefor it is easier to measure Ag+ with precision by use of the Silver ion in solution regardless of halide type or mix thereof. This then determines excess halide, of whatever type, in the coating at the start of the process, and also helps with keeping.
Of course, I like to prewet which normalizes vAg to be about that supplied by city water which actually seems to do nothing with D-76 or HC-110. Now, I have to try Rodinal.
P.S.- Any thing that will filter my coffee will surely stand KOH.
My tap water is eminently suited for drinking because of its good taste and calcium content. It forms a precipitate in most developers that contain carbonate. I don't see that with this version of Metolal, but I have been using demineralized water. If I were to substitute an equimolar amount of p-aminophenol and reduce KOH accordingly, I would see no lingering precipitate. I can try that as soon as my shipment of p-aminophenol arrives.
I hate to try filtering the K2SO4 out of the precipitated metol freebase, but if everything else dissolved, that should tell me something. At the moment, I'm also fresh out of Metol.
When I played the Baroque Oboe with the Governor's Palace Orchestra at Colonial Williamsburg I had the advantage of wearing a wig, so nobody could tell about anything but my music. The oboe has been described as "the ill wind that nobody does good."
Somewhere, you described for Bill the calculation of pH of... (I think)
a KOH solution.
Do you know where it is?
My searches are mute...