Sodium Acetate Buffer pH 5.2 - (Dec/17/2013 )
Does anybody have any specific protocol/recipe for a 3M Sodium Acetate buffer at pH 5.2? I normally dissolve anhydrous sodium-acetate in 150mL of distilled water, adjust the pH with glacial acetic acid (17.416M) and then make it up to 250mL using water but I was wondering if there's a specific way to do it based on pH/pKa calculations rather than having to titrate the acetate in and monitor it via a pH meter.
I've a recipe of 10.5 mL 0.2 M acetic acid solution, 39.5 mL sodium acetate solution and 50 mL water which gives a buffer with pH 5.2. Anyway it's always strongly recommended to check the pH finally and adjust if something is wrong (solutions may be wrongly made, volume errors etc) ...
Don't make it so complicated. Trying to avoid using a pH meter just makes your life more difficult.
1. Make a 3 M sodium acetate solution.
2. Make a 3 M acetic acid solution.
3. Add acetic acid solution to sodium acetate solution (while stirring) until pH is 5.2.
3M solution is way too concentrated for easy calculations (ionic strength starts to play an important role). You can try to calculate buffer composition using thermodynamically corrected pKa value for IS=3 (which is listed as 5.015 in Kotrly and Sucha book). At least it could mean much shorter titration.