Quote Originally Posted by billtroop View Post
Nothing in this thread accounts for the statement, on Rodinal packages, going back several decades, that hydroxide is only 3%.

A 1998 MSDS confirms this; in its entirety it gives

potassium hydroxide, 3%
potassium sulfite, 30-40%
potassium bromide, 1-5%
p-Aminophenol, 1-5%

and the pH is 14 (!!!) - - which is massively higher than other figures, published by Agfa, that we have all seen.
Bill - are you saying you are suprised that a 3% solution of potassium hydroxide has a pH of 14? If so, here's the way to calculate it.

A 3% solution is about 0.53M KOH.
Calculate pOH first:
pOH = -log10[OH-]
pOH = -log10[0.53M]
pOH = 0.276
Then calculate pH:
pH = 14 - pOH
pH = 14 - 0.276
pH = 13.72

A 0.53M KOH solution should have a pH of about 13.7. That's close enough to pH 14 for my book.

If that's not what you are saying, then don't worry, it's my mistake...