Physical Interpretation of Negative pH.

Why are most general chemistry text simply silent on negative pH values
and values greater than 14? In the elementary classes chemistry
students learn that pH are defined from 0-14, but later they are unable
to accept the negative pH concept when by accident they _calculate_ pH
of > 1 M HCl, but of course activity comes into play.
(i) My question is what are common examples (leave aside super-acids)
of solutions having negative pH values and how are they experimentally
measured. Though I never tried, in fear of damaging it, but if I dip
the glass electrode in concentrated 12 M HCl would the pH-meter show
negative values?

(ii) Some people claim that the dissociation is controlled by self
ionization of water and the product [H+][OH-] = 10^-14 always holds
true.
See for example the answer 1 here:
http://www.newton.dep.anl.gov/askasci/chem99/chem99230.htm

(iii) A short note in J.Chem.Ed has a procedure for making a pH
-47 to +47 HCl solution which I think is meant to be a joke.

Suppose we have 1 liter of 1x10^-6 M HCl, add about 99 L of water, the
[HCl] is 1x10^-8 M and pH= 8. Now suppose you have single molecule of
HCl in 10^23 L of water, so that
[HCl] = 1.7x10^-47, the pH is then 47!

Regards,
Farooq.

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