I think the distinction between pH and acidity is starting to get
blurred. Ignoring molal activity coefficients and other such details,
pH is the negative log of the concentration of hydrogen ions in water
and is used for Bornsted acids/bases that donate/accept a hydrogen ion.
The Lewis acids/bases accept/donate electron pairs, which is why
chlorine, being a base, is able to make inert polypropylene acidic. To
stretch this into pH is, in my humble opinion, making quite a leap,
although I have seen even worse transgressions made because "everybody"
understands pH and is comfortable working with that concept.
The story is told (I'd love to confirm this but have been unable to) of
a professor testifying before Congress of the work he had done on a
project, and how proud he was that he how lowered the pH of the waste
from 13 down to 7. The congressperson then asks him: "If you took the
pH from 13 down to 7, why didn't you just take it all the way down to
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