Caffeine and Benzoic Acid in Soft Drinks Many laboratory manuals inchtde lengthy schemes for extraction of caffeine from tea.' A time-saving experiment using No-Doz tablets as the source has recently been described in THIS JOURNAL.^ However, soft drinks derived from the kola,bean, and some that are not, also contain caffeine that can he isolated and purified in as little as 1 hr. In some of the soft drinks that we studied, simple extraction with chlorinated solvents yielded caffeine that was contaminated by relatively large amounts of hensoic acid. Showing a. strong pH dependence (caffeine does not: K. < lo-''; K s < 10-14), benzoic acid can easily he held in t,heaqueous phase, hut i t may he extracted and isolated as s. second product. In such beverages as CocsiCola, Pepsi Cola, Royd Crown Cola, Dr. Pepper, Mountain Dew, Orchard Park Cola (a local brand), and the law-sugar and sugar-free versions of several of these, we found that a 12-0s. can contained 2 S 5 0 mg of caffeine. Half a. can is therefore sufficient for students either to see the crude product, to purify it by sublimation, or even, with some care, to make semiqtmntitative determinations. If larger yields are desired, commercial syrups, . . which are about six times as concentrated, can be used after dilution with equal volumes of water. Depending on the goals of the course and the amount of time available, one of the following procedures can he used.
of Caffeine Only Place half of a 12-oz. can of soft drink in a 1-24 Erlenmeyer flask. If it iq known t o contain sodium benzoate, make basic with sodium carbonate, to prevent extraction of benoaie acid with the caffeine. Add 50 ml of dichloromethane' and swi1.l ~enllyfor at least 5 min. Transfer t o a separatory funnel (commercial or improvised). When nearly all of the bottom layer is clear, drain into a.small beaker, being careful not t o allow any of the aqueous layer to escape. Set on a hot plate in a hood. While this extract is evaporating t,o dryness, a second hatch can be ohlG.ned and comhined with it. Purify the crude solid by sublimation onto 8. smaller beaker of water nested inside the original beaker. A faint, pleasant aroma accompanying some srthlimed yields is not due t o catreine, which is odorless at room temperature.
Isolation of Both Caffeine and Benzoic Acid Select soft drinks containing both of these ingredients. Omit the sodium carbonate addition; instead, acidify with dilute HC1 and proceed as above. Purify t,he crude products hyfradinal sublimation: Prepare a nested beaker as described above, but immerse the set-up partway in s. boiling water bath. After a few minutes, remove t,he sublimed benzoic acid from the inner beaker and continue the sublimation directly on a hot plate.
' We have found that the procedures for extraction from tea, can d s o be greatly simplified by omitting the prior treatment with lead acetate t o remove tannins; these are not extracted by the method described herein. Likewise, sublimation eliminates the need for addition of decolarizing charcoal. Mom, ALFREDL., J. CHEM.EDUC.,49, 194 (1972). Wichloromethane was chosen because it is less toxic than the commonly used chloroform. JOHN A. LASWICIC PATY HALLLASWICK
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Journal o f Chemical Education
