Distillation Case

The objective of this week's lab was to see which method of distillation, simple or fractional, is better at purifying an impure sample into its component compounds. We determined the purity of the component compounds by taking index of refractions, microboiling points, and density measurements on the two different distillates. The two compounds that we were distilling were cyclohexane and toluene. First of all, I had to measure the index of refraction, microboiling point, and density of each initial compound. For the cyclohexane, I determined the index of refraction to be 1.4278 @ 220C, the microboiling point to be 830C-880C, and the density to be 0.786 g/mL. For the initial toluene, I determined the index of refraction to be 1.4961 @ 220C, the microboiling point to be1130C-1160C, and the density to be 0.856 g/mL. Then I continued on to the simple distillation during the first week. For the simple distillation, I combined 14 mL of the each compound with each other in the boiling flask. I started heating the sample and measured the temperature when the first drops of distillate were collected at 810C. I continued on to collect 12 mL of the lower boiling liquid (cyclohexane) at a constant temperature around 900C. Then the temperature rose dramatically to 1090C and then again remained steady. I collected 6 mL of distillate during this transition zone, and continued on to collect 6 more mL of the higher boiling liquid (toluene). Then I determined the index of refraction, microboiling point, and density of the cyclohexane to be 1.4275 @ 220C, 820C-860C, and 0.785 g/mL respectively. I also determined the toluene's index of refraction, microboiling point, and density to be 1.4965 @ 220C, 1110C-1150C, and 0.870 g/mL respectively. Then when I came back to lab the next week, we had to perform a fractional distillation on the same mixture. For the fractional distillation, I combined 10 mL of each component compound into the boiling flask. Again I started heating the sample and collected my first two mL of distillate starting at 81.50C with the first drops and finishing at 830C. I dumped these first two mL out of the collecting graduated cylinder into the waste container. Then, I continued on to collect 4 mL of the lower boiling liquid around 840C. Again I saw a sharp spike in the temperature and collected 1.4 mL during the transition zone. Then, the temperature flat lined again around 1100C, and I continued on to collect 6.5 mL of the higher boiling liquid. I then determined the index of refraction, density, and microboiling point of the cyclohexane to be 1.4265 @ 220C, 0.780 g/mL, and 800C-820C. I also determined the toluene's index of refraction, density, and microboiling point to be 1.4968 @ 220C, 0.865 g/mL, and 1080C-1110C. When comparing the literature values for the index of refraction, boiling point, and density of the two compounds to my own determined values, I found that the samples I collected from the fractional