Fractional Distillation

Fractional Distillation of GSM Blue Pamela Trix Lanaja, Jonathan M. Librojo, Shaun Therence Mabunay and Carissa Mae Magdaleno 3Bio3, Department of Biology,College of Science, University of Santo Tomas, Manila, Philippines Abstract G. S. M. Blue is composed primarily of water, sugar cane alcohol with essences of juniper berries and other botanicals with traces of impurities and flavourings and it has 32. 5 percent alcohol by volume (65 proof). The experiment aimed to separate its components, alcohol and water, and to determine its percent concentration of ethanol by using the Fractional distillation method.

A certain volume (25 mL) of G. S. M. Blue was placed on the distillation set-up and was heated constantly. A certain volume (1. o mL) of distillate was collected in every test tube until the temperature reached close to 95-97 oC. The volume of distillate collected by the end of the distillation was 14. 0mL at 95 oC, giving a percent alcohol of 71. 43% and 4. 0% loss. Introduction In general, beverages may be simply defined as any drink which can relieve thirst, nourish the body, stimulate the appetite or increase the amount of body fluids.

These may be classified as Alcoholic or non-alcoholic. Alcoholic beverages have made an inescapable presence in our culture for centuries either for its hygienic, medical, or recreational purposes. Alcoholic beverages are liquids produced from the alcoholic fermentation of fruits or grains [1]. The sample used in the experiment, G. S. M. BLUE, is a 65 proof, sugar cane alcohol with essences of juniper berries and other botanicals. Its smooth, sweet taste gives drinkers a “light-on-the-chest” feeling without hangover.

Distillation is the separation of a liquid mixture into its components on the basis of difference in boiling points. The liquid is changed into a vapour by boiling. The vapour is pure as other substances are left behind. The vapour is then cooled. It condenses to a pure liquid which is called the distillate. In the experiment, fractional distillation was used for the separation of the components of the G. S. M. Blue. In fractional distillation, a distilling column allows the vapour arising from the distillation pot to be repeatedly recondensed and revapourized.

After a number of these recondensation/ revapourization steps, the lower boiling component will be relatively free of any higher boiling components. This allows for a more thorough separation of the liquids. This method of distillation is employed during the Oil Refining process. In this experiment, the group should be able to achieve the following objectives: (1) to separate and calculate in percentage the alcohol content of a commercial alcoholic beverage (G. S. M. Blue) by distillation process, and (2) to compare the efficiency of simple and fractional distillation techniques.

Results and Discussion In the experiment, quick-fit apparatus was used. The components of quick-fit apparatus are (1) distilling flask, where the sample is placed, (2) still head(distilling head), it holds the thermometer to allow the temperature of vapours to be monitored during the distillation, (3) condenser, a tube surrounded by a water jacket to cool and condense vapours, (4) thermometer, measures the temperature, (5) receiver adapter, connects the condenser and receiver, (6) test tubes, where the distillate is placed. [2 & 3]. Refer to Fig. 1. Figure 1.

Quick-fit apparatus Fractional Distillation In a Distilling flask contains the sample and 3 pieces of boiling chips. The boiling stones are small, irregularly shaped stones added to liquids to make them boil more smoothly. They provide nucleation sites so the liquid boils easily without becoming superheated. The heating of the flask should be slowly rotated. When the solution boils, a ring of condensate rising up the still head can be observed. If heating is too rapid and the condensate is pushed too rapidly, equilibrium between liquid and vapour will not occur and eparation of the components will not be satisfactory. If the flask is heated too strongly before the distilling head has been warmed by hot vapours and condensate, the still head may flood, or shows an excessive amount of liquid in one or more portions. [5]. The following table shows the result from the fractional distillation: Table 1. Results of Fractional Distillation Test Tube #Volume (ml)Temperature (°C)Flame Test 0050 1168+ 2274+ 3376+ 4478+ 5579+ 6680+ 7782+ 8884+ 9986+ 101088+ 111190- 121292- 131394- 141495-

Table 1 shows the results of the boiling temperature and flammability test for fractional distillation. The volume of the distillate collected was 14 ml and the volume left in the flask was 10 ml. It also shows that as the volume of distillate increase, the temperature also increases until it comes to a point wherein the temperature closes to 100oC. In this experiment, two distinct fractions are obtained. The first corresponds to the component with the least boiling point which is separated first, and the second corresponds with the highest boiling point that is drawn off at the last.

The component with the highest boiling point can be distilled and redistilled until it becomes pure [3]. According to Dalton’s Law of Partial Pressure, a mixture will only boil if the sum of the two partial pressures is equal to the atmospheric pressure. And according to Raoult’s Law, the partial vapour pressure of a mixture in an ideal solution is equal to the vapour pressure of that pure mixture times its mole fraction in the liquid. A mixture must not have a mole fraction of water that is 0. 7 because it will not boil at 100oC and is less than atmospheric pressure.

The concept of Dalton’s and Raoult’s law is that the vapour composition above a mixture is dependent both on the vapour pressures of the pure compound and on their mole fraction in the mixture [3 & 5]. In the flammability test, the 1st- 10th test tubes produced a blue flame which means that ethanol is present in the those distillates, while in the 11th – 14th test tubes, there was no flame produced because alcohol was removed. It shows that as the distillation of the sample continues, there is a decreasing amount of alcohol being gathered in the separate test tubes.

The first test tube contains more alcohol compared to the last test tubes used which contain the last few drops of distillate. Figure 2. Temperature as a function of volume Figure 2 shows that as the volume of distillate collected increases, the temperature also increases. When the temperature reached close to 100oC, the temperature stopped from rising and is constant. In this distillation, in the first drop of the first test tube, with 0 mL, the temperature was 50°C. When it reached 1. 0 mL, the temperature was 68°C. In test tube #2 with a volume of 2. mL, the temperature was 74°C. In test tube #3 with a volume of 3. 0 mL, the temperature was 76°C. In test tube #4 with a volume of 4. 0 mL, the temperature was 78°C. In test tube #5 with a volume of 5. 0 mL, the temperature was 79°C. The temperature increased from 80°C to 82°C in test tube #s 6 and 7 with a volume of 6. 0 mL and 7. 0 mL respectively. In test tube #8 with a volume of 8. 0 mL, the temperature was 84°C. In test tube #9 with a volume of 9. 0 mL, the temperature was 86°C. The temperature increased to 88°C in test tube #10 with a volume of 10. mL. In test tube #11 with a volume of 11. 0 mL, the temperature was 90°C. In test tube #12 with a volume of 12. 0 mL, the temperature was 92°C. In test tube #13 with a volume of 13. 0 mL, the temperature was 94°C. In the last test tube with a volume of 14. 0 mL, the temperature was 95°C. After performing the flammability test, the percent alcohol and percent loss can then be computed using these formulas. % Ethanol=(volume of distillate(+)with flame test)/(volume of sample) ? 100 % Loss =vol of sample- ((vol. of residue+vol. of total distillate)/(vol. f sample) x 100 And so, using the formulas above, 71. 43% ethanol and 4. 0% loss was computed. Therefore, the percent alcohol of the sample is 71. 43%. The percent loss was 4. 0 %, This explains that there is some part of the sample that is loss which was caused by evaporation due to the constant heating of the flask. The percent loss also shows that there is an excessive heating of the flask that caused the rapid evaporation of the sample or it can be caused by the mishandling of the test tube that caused to the careless collection of distillate [7].

Simple distillation is used in separating components of liquid mixtures, which have boiling point more than 25? C from each other at one atmospheric pressure. Fractional distillation separates liquid much better than simple distillation because of the glass beads in the fractionating column. Simple distillation gives poorer separation than fractional distillation for it provides theoretical plates on which the refluxing liquid can condense re-evaporate and condense again, essentially distilling the compound over and over again. [3, 5 &7]. Experimental

The set-up was assembled and the joints were greased well to prevent vapour loss. G. S. M. Blue (25 ml) and 3 pieces of boiling chips were placed in the distilling flask. The temperature was recorded on the first drop of distillate. One ml of distillate was collected in a separate numbered dry test tube while the temperature was recorded. This was repeated until the temperature reached 95-97°C. A different numbered dry test tube was used at each fraction. The test tubes were flame tested in descending order. Watch glass was used for the flame test. The result in the flame test was recorded.

References [1] Gatchalian, M. M. & de Leon, S. Y. (1992). Introduction to Food Technology. Metro Manila, Philippines: Merriam & Webster, Inc. [2] Mayo, D. W. , Pike, R. M. & Trumper, P. K. (2000). Microscale Organic Laboratory. 4th ed. New York: John Wiley & Sons, Inc. pp. 617-651. [3] Pavia, D. I. , et. al. (1999). Introduction to Organic Laboratory Technique: A Microscale Approach. pp 22-54. [4] Russell, C. A. (2000). Chemistry, Society and Environment: A New History of the British Chemical Industry. Royal Society of Chemistry. pp. 69. [5] Fessenden, R. J. , Fessenden, J. S. Fiest, P. (2001) Organic Laboratory Techniques. 3rd ed. California, USA: Brooks/Cole. pp. 77-96. [6] Retrieved June 27, 2011 from the World Wide Web: http://www. associatepublisher . com/e/v/vo/vodka. htm. [7] Retrieved June 27, 2011 from the World Wide Web: http://www. pharmpedia. com/Distillation. Appendix % Ethanol=(volume of distillate(+)with flame test)/(volume of sample) ? 100 % Ethanol= 10ml/(14 ml) ? 100 % Ethanol=71. 43% % Loss =vol of sample- ((vol. of residue+vol. of total distillate)/(vol. of sample) x 100 % Loss = (25 mL-(14 mL+ 10 mL))/(25 mL) x 100 % Loss=4. 0%

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