March 09, 2004
As long as the pH meter is available...
Today in lab, a couple of people broke the "no food or drinks in lab" rule. My prof - whose lab desk is next to my lab bench - and I reacted not by stating the obvious, but by saying, "Hey! Let's measure the pH of those drinks!" Why not? We all had $600 Accumet pH meters in front of us. So, we measured the pH of the following solutions:
- Gatorade X-Factor: pH 3.089
- Arizona Iced Tea brand Green Tea w/ Ginseng & Honey: pH 3.424
That's pretty interesting, since at first approximation, I'd expected any Gatorade solution to be isotonic, at a physiologic pH of ~7.42 or so. Not so, but given that the ingredients label lists citric acid and its conjugate base sodium citrate (a buffer solution), no big surprise: it's almost exactly the pH of a 0.100 M solution of acetic acid (a weak acid, with a Ka of 1.737 x 10^-5). The Arizona Iced Tea also has citric acid in its ingredient list, but no conjugate base listed (though it undoubtedly exists in solution).
Posted by Russell Whitaker at March 9, 2004 09:43 PM | TrackBack