Caffeine And Green Tea Lab Report

In this lab, caffeine was extracted from black tea, and green tea through a vacuum filtration, and a rotovap. The melting point of the sample of black tea was 219.12-236.05 ˚c, and for the green tea it was 176.22-227.6 ˚c. The % error of the melting point indicates how much error there was from the melting point taken experimentally. The % error of the melting point for black tea was 0.44%, and for green tea it is 3.15%.Since the theoretical melting point of caffeine is between 235-237 ˚c, we can indicate how much error the experimental melting point had. The melting point range was pretty broad for both teas by at least 40 ˚c. This indicates the impurity of the caffeine extracted with its tannins. Tannins are what give the caffeine its color, and when it is not isolated from the caffeine it creates a soluble salt in water when mixed with Na2CO3. The reason the melting point would be broader is because tannins decompose above temperatures of 200 ˚c, thus making the melting point higher.
The results were obtained, the final mass of the caffeine for the black tea was 91.6 mg,
the results calculated for green and black tea were much closer to the accepted value than all the comparable results calculated for green and black tea . Black tea had the most caffeine, and the green tea had the least. This is make sense, as usually the black tea has more caffeine in it, as black teas are fermented making them have more caffeine in them. This can be seen from table 2 in which the black tea had a higher melting point range of 204.7-241.7 ˚c, while black tea had 191.3-239.9 ˚c. However, there is source of error that may have contributed to the 2. 85% and 2.05 %. For this experiment could have been from mishandling the equipment, not weighing the correct amount of tealeaves, allowing other substances in, or not performing the extraction