CHM 236 Lab
Individual Writing Assignment
February 23, 2015
Extraction and Sublimation of Caffeine
Table of Reagents:
During this experiment there were two parts performed. The first part of the experiment was extraction. During this part we were assigned to extract the caffeine out of the tea leaves. Once the extraction process was complete, we calculated the percent yield. The percent yield is calculated based on the theoretical yield and the actual yield we got during the experiment. Our percent yield from extraction came out to be around 50%. We got these results by using 55 mg of caffeine extracted from the 3,900 mg of tea present and dividing it by the theoretical yield of 110 mg of caffeine. After that we multiplied the quotient by 100 to give us 50% yield. This yield is a very low extraction rate. One possible reason for the low rate could have been due to a pretty large spill of the caffeine solution during our experiment. Because of that spill we lost a good amount of the caffeine that could have been extracted. Another error that could have occurred in our experiment was when the suction funnel was too small for our caffeine solution and had to be transferred to another bigger suction funnel. The second part of the experiment was sublimation. During this process we used the caffeine extracted from the previous experiment and purified the caffeine. The 55 mg of caffeine we extracted was purified during the sublimation process. Our end result after sublimation came out to be 24 mg of pure caffeine. This amount was calculated by weighing the watch glass that the pure caffeine was placed on first. Then we measured the watch glass plus the pure caffeine together. The combined amount of the watch glass and the pure caffeine came out to be 25.80 mg. Then we subtracted the total weight from just the watch glass weight and got 0.024 g or 24 mg or pure caffeine. Our sublimation yield was calculated by dividing the 24 mg of pure caffeine by the 55 mg of crude caffeine and multiplying it by 100. Our percent yield came out to be 43.64%. This is a very high percent yield. The high percent yield could be due to the fact we had to add around 25 mg of pure caffeine to our sublimation apparatus because the crude caffeine was not subliming like it should. If these few little errors had not occurred the percent yield should have been around 10%.
The last part of our experiment was to find out the melting point of our pure substance. If the results match the melting pointing of pure caffeine then we correctly conducted the experiment. The melting point range of