Extraction and Sublimation of Caffeine
By: Ashley Barnes
CH 236 – P8
Experiment 4 & 4.5
Table 1. Table of Reagents
Discussion The extraction yield refers to the percent of caffeine in the tea leaves at start of the extraction experiment. Tea leaves had 0.55 grams of mass per eight ounce serving. The weight of the extracted crude caffeine was 0.264 grams. Therefore, the extraction yield was 48%. This means that we pulled out almost half of the caffeine in tea leaves. When an extraction is carried out under optimal conditions, up to 80% of crude caffeine can be extracted .
In reflection, more caffeine could have been extracted if the tea leaves would have steeped a few minutes longer at a higher temperature. This could have been one error made while preparing to extract caffeine. During extraction process in separatory funnel, solvents were not mixed vigorously, this could result in lower surface area between the layers. The layers separated into two distinct layers, however, more time could have been allotted to ensure the water-soluble impurities were pulled away . After extracted caffeine was dried, green solid was noted on the bottom of the filter flask, also known as the crude caffeine. The sublimation yield refers to the percent of caffeine sublimated from the crude caffeine. This percent is calculated by dividing the mass of pure caffeine (0.009 grams) by the mass of crude caffeine (0.264 grams), and multiplying it by 100. This results in a sublimation yield of 3.4%. If sublimation of caffeine occurred under optimal conditions, more mass of pure caffeine would have sublimated, resulting in a higher sublimation yield. Optimal conditions refers to the process of more mass of caffeine changing directly from solid to the gas phase, ultimately forming a white solid . After the caffeine sublimated, the mass of pure caffeine was calculated by subtracting weight of the filter flask before and after.
References: 1.) Weast, R., CRC Handbook of Chemistry and Physics, 58th Edition; CRC Press, Inc.: Cleveland, OH, 1978. 2.) Barboro, J., Hill, R., Experiments in Organic Chemistry, 3rd Edition; Grantham, C.: Raleigh, NY, 2005. 3.) Hampp, A., Extraction of Caffeine from Tea: A Modification of the Procedure of Murray and Hansen. J. Chem. Educ., 1996, 73 (12), p 1172.