Quote Originally Posted by gainer View Post
Correct me if I'm wrong, but I seem to remember learning that pH=14 does not necessarilly mean that the solvent that is causing that pH is saturated. In the case of strong alkalis, pH=14 may occur far below saturation, but cannot increase as more alkali is added. An acid-base reaction may occur in a strong solution of KOH and go to completion, leaving the pH at 14, with capacity remaining for more such reactions.

What happens to pH when we add just enough KOH to an amount of paraminophenol to form the potassium paraminophenolate? It seems to me that pH>7 implies that more than enough KOH was added, but even pH=14 does not tell us how much more.
Spot on Patrick, you understand what I'm getting at.

It's the fact that the "potassium paraminophenolate" in a high concentration Potassium Sulphite solution has a pH of around 11.8 and when we have excess of hydroxide as in the more modern Rodinal formula we go to pH 14

pH 14 is in fact listed as being reached by 5.6% KOH solution, the MSDS's for A&O Rodinal show the KOH is only 2.7%. But 0.5% KOH is pH 13 and the Sulphite is pH 9-10 anyway so every thing there seems as expected.

Ian