From what I can interpret, it means making a 8mM Ammonium chloride stock solution using Deionized water, then gradually adding ammonium hydroxide (28%, 14M) until the pH meter reads 9 or 10 pH. Is that correct? Should the approximate percent of ammonium hydroxide required to reach each pH be determine first then added all at once, or should I gradually add it in until its approximately the pH on the meter? What determines the molarity of solutes required when making buffer solutions?
I think you are probably preparing the solutions as intended. Ammonium chloride is the salt of a weak base and a strong acid, so it is acidic. You need to add base to raise the pH. Using ammonium hydroxide makes sense since it avoids adding any other cations than ammonium. Of course, the final ammonium ion concentration will be higher than 8 mM, but the chloride concentration will be unchanged. You may want to start with a solution that is a bit more than 8 mM, since there will be a little dilution, then dilute it back to 8 mM once the pH is adjusted. I suggest using 1 M ammonium hydroxide instead of 14 M. It's less unpleasant.
Dear Brandon,
as of my experience, ammonium Chloride is added to washing solutions after fixation of biological tissue to block free aldehyde groups in the tissue left chemical after fixation proper.
For me your formulation "adjusting 8mM Ammonium Chloride to solutions of pH of 9 and 10" makes no real sense to me (ok, I am no chemist...for me that should be then "to make solutions of pH 9, ...." ....would it be possible that you "cite" the complete text / original sentence of a / your recipe and let us know about its context? If it is true that you have to titrate an 8mM Ammoniumchloride (solution) to end up with a pH of 9 or 10, Adam B. Shapiro is certainly right... Thank you !
PS: http://www.pharmaguideline.com/2010/09/preparation-of-buffer-solutions.html :
Pharmaceutical guidelines / Preparation of buffer solutions: scroll down and find
Ammonia-ammonium chloride buffer -
Ammonia buffer pH 9.5 - Ammonia buffer pH 10.0 - Ammonia buffer pH 10.5.
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