Crude Caffeine Sublimation
At the start of the experiment, there was a total of 2.25g of caffeine (the net weight of the tea bag). After preparing the tea solution, extracting, drying and evaporating the weight of crude caffeine was .0321g, making the percent recovery before sublimation 1.43%. After sublimation the weight of pure caffeine was .0027g, making the percent recovery of caffeine after sublimation .12%. The percent recovery of caffeine is less in the second half of the experiment because the crude caffeine had some impurities in it which were taken out by the process of sublimation. The average cup of black tea has about .014g to .07g of pure caffeine in it (MayoClinic 2014). The weight of the crude caffeine fell within the normal range of caffeine in
…show more content…
In this lab, sublimation was used to purify the crude caffeine obtained prior to sublimation. The process of sublimation does this by using the boiling points of compounds. Caffeine has a lower vaporization temperature than other impurities that could have been in the solid crude oil. This makes the gaseous caffeine separate from the other impurities that do not vaporize at that temperature. The sublimation apparatus that was used in this experiment had a cold finger, vacuum, and constant source of cold water. The bottom of the sublimation apparatus was heated at 226˚C, a temperature that enabled the caffeine to vaporize and not the other impurities. The vacuum collected the vaporized caffeine and the cold finger (constant flow of cold water in the apparatus) cooled the gaseous pure caffeine into a solid substance that collected on the bottom of it. The pure caffeine crystals that were attached to the bottom of the cold finger were milky white in color and they appeared as a powder. Once the pure caffeine crystals were obtained, the melting point of them were obtained by using a Mel temp apparatus. The actual melting temperature of caffeine is 236.2 ˚C, and the experimental melting temperature of caffeine was 2.10 ˚C -222.1 ˚C (ChemPub 2016). The melting temperature of the experimental caffeine is lower than the actual melting point of caffeine which means that there had to be some impurities in the experimental pure
In this lab, sublimation was used to purify the crude caffeine obtained prior to sublimation. The process of sublimation does this by using the boiling points of compounds. Caffeine has a lower vaporization temperature than other impurities that could have been in the solid crude oil. This makes the gaseous caffeine separate from the other impurities that do not vaporize at that temperature. The sublimation apparatus that was used in this experiment had a cold finger, vacuum, and constant source of cold water. The bottom of the sublimation apparatus was heated at 226˚C, a temperature that enabled the caffeine to vaporize and not the other impurities. The vacuum collected the vaporized caffeine and the cold finger (constant flow of cold water in the apparatus) cooled the gaseous pure caffeine into a solid substance that collected on the bottom of it. The pure caffeine crystals that were attached to the bottom of the cold finger were milky white in color and they appeared as a powder. Once the pure caffeine crystals were obtained, the melting point of them were obtained by using a Mel temp apparatus. The actual melting temperature of caffeine is 236.2 ˚C, and the experimental melting temperature of caffeine was 2.10 ˚C -222.1 ˚C (ChemPub 2016). The melting temperature of the experimental caffeine is lower than the actual melting point of caffeine which means that there had to be some impurities in the experimental pure