Isolation lab manual) | 236| | Percent
Isolation of Caffeine from Tea (12A) Introduction When a person drinks tea or coffee, it is not pure caffeine. It also has other natural substances.
The purpose of this lab was to isolate caffeine from tea leaves. The methylene chloride removed nearly pure caffeine from the basic tea solution. Caffeine is a white, crystalline, bitter alkaloid, C8H10N4O2 , usually derived from coffee or tea. Caffeine is used in medicine chiefly as a nervous system stimulant. Caffeine is used by humans to ward off drowsiness and restore alertness. Caffeine constitutes as much as 5% by weight of the leaf material in plants.The hypothesis for this experiment is that the observed melting point of the pure caffeine will be lower than the melting point of pure caffeine listed in the lab manual.
Data | Weight (g)| Tea with bag and string| 2. 5160| Tea leaves| 2. 3702| Erlenmeyer flask w/ vacuum| 38. 365| Erlenmeyer flask w/ vacuum w/ crude caffeine | 38.
414| Crude caffeine| 0. 0490| Pure caffeine| 0. 0286| | Melting Point (°C)| Percent recovery/yield| Crude caffeine| 214-215| 2. 067| Pure caffeine| 205-207| 1.
207| Pure caffeine ( in the lab manual) | 236| | Percent error: 12. 71% Discussion of Results:The hypothesis was proved. The melting point of the pure caffeine that was obtained from the experiment was lower than the literature value (236°C). This hypothesis was a good hypothesis because there are some explanations as to why the melting point would be lower.
One reason is, the purification process was not perfect, and there were impurities in the caffeine affecting the melting point. The melting point depresses due to impurities in the sample. The results obtained were expected since, it is known that tea is not 100% caffeine and the caffeine would not be 100% pure in the end. The ercent recovery of the pure caffeine was not going to 100% since caffeine constitutes as much as 5% by weight of the leaf material in plants.
The results were accurate because the experiment was done carefully. The percent error is reasonable. It was known that the melting point would not be exact. Conclusion: In consideration of the numerous sources of error, this experiment has been a success.
Pure, or mostly pure, Caffeine crystals have been isolated from tea and weighed. This value was similar to the accepted Caffeine content of tea, thus the results supported the original hypothesis.