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This article is from the Chemistry FAQ, by Bruce Hamilton B.Hamilton@irl.cri.nz with numerous contributions by others.

31.19 What is the pH of Coca-cola?

Phosphoric acid is an approved food-grade acid that is added to Coca-cola

to provide some of the taste. When CO2 is added to "carbonate" aqueous

solutions, carbonic acid is formed. A tin of coca-cola was cooled in a

refrigerator to 7C and the pH of the sample measured over time. The pH

electrode was not temperature-compensated, so a correction was applied.





Time pH pH (when opened) (corrected) Initial 2.75 @ 7C 2.6 30 seconds 2.78 @ 7C 2.6 60 seconds 2.80 @ 7C 2.6 2 minutes 2.82 @ 7C 2.7 4 minutes 2.80 @ 7C 2.6

pH Degassed pH 2.52 @ 21c RT sample 2.50 @ 20C

A sample was degassed in an ultrasonic bath for several minutes and thepH measured, and compared to a control sample maintained at the sametemperature and time profile.So the conclusion is that the pH of Coca-Cola is approximately 2.5 - 2.7.Not surprisingly, the relatively weak carbonic acid from the dissolved CO2did not significantly affect the pH of the beverage. The aluminium beveragecontainers are lined with a thin polymer or lacquer coating to prevent thealuminium metal dissolving into the beverage.Note that the differing flotation characteristics of cans of the normalversions of carbonated beverages like Coca-Cola ( they may sink ), andthe diet versions ( they may float ), has nothing to do with the amountof CO2 present. It is due to the increase in solution density from thefew percent of sugar added to the normal version, while the diet versionhas only a few hundred ppm of an artificial sweetener that is much sweeterthan sugar.



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