Peter,
This is a cannard that has been recently published in the
photographic press by one of your countrymen. Amidol works in an acid
condition as a reducing agent when the pH is very much lower than what is
encountered in a typical stopbath (about pH 2.4-2.7) In an acid bath above
this range (4.5-5.5 of most stopbaths) it barely reduces at all. pH 6.8 and
below will slow it down to a crawl. The often heard remark "it works in an
acid condition" needs to be qualified-yes it will, but only if the solution
is REALLY acid. I would suppose few darkroom practioneers would choose to
use HCL or sulfuric acid as an accelerator for amidol. A citric acid
stopbath will satisfactorily work with prints developed in amidol.
Maxim M. Muir