Caffeine Isolation Lab I. Abstract Solid crude caffeine was extracted from tea and purified via sublimation. The melting point was experimentally found at 215. 9-218. 7oC. II. Introduction Caffeine is the most dangerous substance being used in lab this semester, but it’s also one of the most favorite chemicals commonly ingested among college students. The main purpose of this lab was to extract caffeine from a beaker of about 20 ml of tea.
Sublimation was an effective and convenient final method of purification, because it required no additional chemicals to be added or mixed into the caffeine. III. Procedure See lab notebook, pages 84-85 IV. Results and Discussion After the final sublimation, the total mass of extracted caffeine was 11. 7mg. The other 43. 3mg the manufacturers’ claim to be in a cup of tea were most likely lost throughout the experiment, either through transferring between containers, leaving some caffeine behind in the tea leaves, or not pipetting out all of the organic matter after the tubes were centrifuged.
The melting range for the crude caffeine was 215. 9-218. 7oC. Although this melting range is lower than the MSDS value, this was expected and stated in the lab manual. V. Conclusion We successfully extracted 0. 0117g of solid crude caffeine from a brewed beaker of tea, and found the melting point to be lower than the literature value given. The percentage yield for this experiment (based on the manufacturers’ claim of 55mg per bag of tea) was 21. 27%. It was also determined that from 2. 2894g of tea leaves, caffeine only contributed to 0. 511% of that weight. VI. Extra Questions 2. The sodium bicarbonate was added to dissolve the tannins and gallic acid present in the tea in order to extract purer caffeine. 3. The green tinge of the crude caffeine is the result of the presence of chlorophyll and other water soluble compound found in the tea. 4. The melting point was most likely lower than 236oC because it was not an entirely pure substance, and still held some of the other chemicals previously added. 5.
If calcium carbonate was instead used to remove the tannins/gallic acid, the mixture could be filtered into a new container to catch all the insoluble calcium salts. DIH2O would be poured over the salts to attempt to get all the tea through the filter. 6. If the sublimation step was performed at atmospheric pressure, additional heat would be needed and some of the caffeine might decompose. 1. Solid carbon dioxide is called dry ice because it directly sublimates to a gas and skips melting into a liquid. When heating solid water, it first melts into a liquid and then turns into a gas.
One may have liquid carbon dioxide at pressures above 5. 1 atm. 3. The solid would remain in a solid state until the temperature reached 80oC, where it would then sublime into a gas. 4. The solid would remain in a solid state until the temperature reached 100oC, where it would then be a liquid. 5. To sublime the substance, the surrounding pressure would be to be dropped below 50 mm Hg at the boiling point of the substance. (from lab)- As a 134 lb. person, it would take approximately 140 cups of tea to reach my lethal dose.