Caffeine Lab

Record/Data:

Weight of tea bag = 2.3643g

Weight of tea used = 2.3643g *3 = 7.0929g

Filter flask weight = 79.1895g

Crystals in filter flask = 79.3601g

Caffeine recover = 79.1895g – 79.3601 = 0.1706g

Caffeine recovered per bag of tea = 0.1706g / 3 bags = 0.0569g (1000mg/1g) = 56.9mg

Melting point = 225-228 ºC

Caffeine pre gram of tea = 0.1706g caffeine / 7.0929g of tea = 0.0241g (1000mg/1g) = 24.1mg

Conclusion:

During this lab we first note that the organic layer remains on the bottom due to the difference in density between water and the dichloromethane holding a density of 1.33 g/mol. We also learn that the ice in the test tube would melt prior to the formation of the caffeine crystals, and that condensation of the air on the inside of the flask was not taken into consideration. The crystal first began to form around the neck and vent of the flask as feathers. We fine that ≈56.9mg of caffeine could be recovered per bag of tea. This would suggest that there is 0.024g per 1g of tea or 24.1mg per 1g of tea. The literature had a melting point of 238ºC and my melting point during the lab was 225-228 ºC, letting me know that although my sample was close it was not completely pure. The tea leaves we use have acidic properties by nature and we would contaminate our sample with these properties if we extract directly with the dichloromethane.