Quote Originally Posted by Kirk Keyes View Post
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...
The MSDS, of course, only mentions what you will find by analysis of the product, not what is put into the product. A considerable amount of KOH goes into the formation of the potassium aminophenolate. I do not know the pH of a solution that originally contained only enough KOH to make the p-aminophenol base soluble as the phenolate, but my attempts to make such a solution have measured in the 12-13 region. The 3% spec is surely an excess, not the total amount put in.

One can make a solution of KOH from K2CO3 and Ca(OH)2 in water. A slight excess of Ca(OH)2 would assure no carbonate in the solution, but perhaps a little of the calcium hydroxide. Any comment?