Organic Chemistry Laboratory Formal Report
Determination of percent ethanol and percent loss in Sombrero Tequila using simple distillation
CHEMISTR Y
200 L
Maria Patricia R. Moran*, Serra Nicole Marcelino, Miguel Gabriel Ocampo, John Edward Paz Department of Biological Sciences, College of Science
*Corresponding author; e-mail:
[email protected]
Abstract In this experiment, the percent ethanol and percent loss was calculated through simple distillation of a 20mL sample of Sombrero Tequila and a flammability test. After the distillation process, 12.5mL of distillate was collected at 98°C. Through the conduction of the flammability test, it was determined that 6.0mL of ethanol was collected. After the necessary computations, the percent ethanol was determined to be 30% and the computed percent loss was 36.25%.
Keywords: simple distillation, flammability test, percent ethanol, percent loss
Introduction Alcohol is a very important compound with varied functions ranging from commercial, medical and even industrial uses. This compound is a family of organic compounds with the characteristic functional group of hydroxyl (OH) (Figure 1) attached to a sp 3hybridized carbon (Klein, 2012).
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Organic Chemistry Laboratory Formal Report
Figure 1. Structure of ethanol
One of the earliest applications of distillation would be concentrating the alcohol content of alcoholic beverages. Tequila is an example of an alcoholic beverage called “spirits” that is of Mexican origin and are made from the distillation of fermented juice of agave plants. The alcohol content of spirits range from 40-50% that is very much higher compared to wine (8-14%). Ethanol, a type of alcohol, is considered to be the active ingredient on alcoholic beverages (Figure 1). Production of ethanol usually involves fermentation, a process of metabolism of carbohydrates by yeast in an anaerobic environment. Unfortunately, excessive intake of these alcoholic beverages may produce biological effects that may harm the body. Liver damage may one of the leading effects of alcoholism that include symptoms of fever, abdominal pain and jaundice, or the yellowing of the skin. Drinking alcohol in moderation is found to have a beneficial effect on the heart, yet abuse would entail an increase in the blood pressure and an increased risk for heart attack and stroke. Mild effects would include heightened mood, slurred speech and delayed reaction times that could lead to violence or inappropriate behavior (NHMRC, 2009).
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Organic Chemistry Laboratory Formal Report Distillation is a method of separating liquids that has been practiced for thousands of years. Specifically, distillation is the process of separating compounds through the utilization of the differences in volatility, or the tendency to vaporize, of the liquids (Winkle, 1967). The basic principle of distillation concerns that the vapor produced through heating has a different composition compared to the liquid. Since the more volatile liquid is more likely to be vaporized first, the vapor produced is richer in terms of the more volatile component compared to the liquid (Palleros, 2000). Conversely, the less volatile component is richer in composition in the liquid. Ethanol boils at 79°C and water boils at 100°C. Therefore in this experiment, ethanol would be considered as the more volatile component and water as the less volatile component. Basically, there are two types of distillation: simple and fractional distillation. A simple distillation consists of a round-bottom flask, where the liquid is placed, distillation head, which connects the flask to the condenser, with a thermometer and an adapter that connects condenser to the receiving flask (Palleros, 2000). The set-up for simple distillation is shown in Figure 2.
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Organic Chemistry Laboratory Formal Report
Figure 2. Simple distillation set-up
Figure 3. Fractional distillation set-up
As for the fractional distillation, the same set-up as with simple distillation is also required but there is an addition of a fractional column that is to be inserted between the
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Organic Chemistry Laboratory Formal Report distillation flask and distillation head. This fractional column functions to provide a larger surface area for the mixture to be constantly vaporized and condensed (Palleros, 2000). One major difference between the two is that the simple distillation works efficiently with volatile liquids whose boiling point difference is very large usually of about 25°C. Furthermore, it is advised that fractional distillation should be used when the boiling point difference is lower than this value. Distillation is a very cheap and convenient method of separating liquids in mixtures, yet one major disadvantage could be seen when handling liquids with very small difference in volatility or boiling point. The purpose of this experiment is to separate and calculate in percentage the alcohol content of a commercial alcoholic beverage, Tequila Sombrero, by distillation process and to compare the efficiency of simple and fractional distillation techniques. Results and discussion The table below shows the results of the conducted experiment, both the distillation process and the flammability test. Table 1. Volume, temperature and flammability test results of the distillate
Test Tube No.
Volume of Distillate (mL)
Temperature
Flammability Test
1
0
60°C
+
1
0.5
73°C
+
2
1.0
78°C
+
3
1.5
80°C
+ 5
Organic Chemistry Laboratory Formal Report 4
2.0
81°C
+
5
2.5
81°C
+
6
3.0
81°C
+
7
3.5
81°C
+
8
4.0
82°C
+
9
4.5
83°C
+
10
5.0
83°C
+
11
5.5
84°C
+
12
6.0
85°C
+
13
6.5
87°C
-
14
7.0
88°C
-
15
7.5
90°C
-
16
8.0
92°C
-
17
8.5
94°C
-
18
9.0
95°C
-
19
9.5
97°C
-
20
10.0
97°C
-
21
10.5
97°C
-
22
11.0
97°C
-
23
11.5
98°C
-
24
12.0
98°C
-
25
12.5
98°C
-
Table 1 shows the direct relationship between the volume of the distillate and temperature. Therefore, as the volume increases, the temperature also increases. As observed in the results of the flammability test, there is a clear distinction between the 6
Organic Chemistry Laboratory Formal Report 12th and 13th test tubes that is indicated in red ink. A “+” sign was recorded up until the 12th test tube since the distillate produced a blue flame. This entails that up until the 12th test tube, ethanol is the more dominant compound of the distillate; knowing that ethanol is flammable. As the distillate reaches the 13th test tube, a “-“ sign was recorded to signify that there was no flame produced. This could be explained by the fact that water became the more dominant thereby prohibiting the distillate from being flammable. Therefore, as the distillation process continues, the amount of ethanol produced in the distillate decreases (Palleros, 2000).
Figure 4. Relationship between temperature (oC) and volume (mL) of the distillate
Figure 4 shows the graph of the temperature in relation with the volume of the distillate. It can also be observed that towards the end of the graph where the temperature is nearing 100°C, the temperature stopped increasing and remained constant. This constancy is called azeotrope, which is a mixture of two liquid that has a constant 7
Organic Chemistry Laboratory Formal Report boiling point and composition throughout the distillation process. The azeotrope has a lower boiling point compared to the either of the individual components, so it should be completely distilled before the distillation of the excess component occurs (Pastos, 1998). Under distillation, two principles are present, namely: Dalton’s Law and Raoult’s Law. Dalton’s law of partial pressure states that for a mixture to boil, the sum of the partial pressures must be equal to the atmospheric pressure (Chang, 1986). On the other hand, Raoult’s law states that the change in vapor pressure of a substance can be determined by the product of the mole fraction of the substance multiplied by the vapor pressure of the pure substance. The formulas used for computing the percent ethanol and the percent loss were:
Using the formulas above, the percent alcohol obtained was,
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Organic Chemistry Laboratory Formal Report
and the percent loss was,
Therefore, it was computed that the percent ethanol was 30% and that the percent ethanol lost was 36.25%. This percent loss may be attributed to different sources of error such as the mishandling of the distillate, excessive heating of the flask or evaporation. In conclusion, using fractional distillation is a much better option compared to simple distillation especially if handling liquids with close boiling point difference. The difference in boiling point of the two compounds (ethanol and water) would be 22°C, therefore it should be requiring a fractional distillation set-up. Fractional distillation gives a much better separation of liquids since there is repetition of the vaporization and condensation process.
Experimental methodology Before the conduction of the experiment, the necessary materials were gathered such as the quick-fit distillation set-up, Sombrero Tequila sample, Bunsen burner, two boiling chips, thermometer and test tubes. All test tubes were calibrated 0.5mL using a marking
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Organic Chemistry Laboratory Formal Report pen. The set-up for simple distillation (Figure 2) was assembled, where glycerol was used to grease the joints to avoid vapor loss on the duration of the experiment. In the pear-shaped distilling flask, 20mL of the Sombrero brand tequila together with two boiling chips was placed. Using a Bunsen burner, the distilling flask was heated with the flame constantly being rotated around the flask.
As the first drop of distillate was
collected in the first test tube, the initial reading for the temperature was recorded. Then, 0.5mL of the distillate was gathered and the corresponding temperature was recorded. In the same way, 0.5mL of the distillate was collected in the succeeding test tubes and the corresponding temperature was simultaneously recorded. The flame was removed after the temperature reading reached 98°C to avoid the vaporization of water. The set up was cooled and the remaining liquid, also known as the residue, was poured into a graduated cylinder. The volume was recorded. As for the distillate contained in the test tubes, two drops of each were placed on a watch glass and underwent the flammability test, where a match a was used to see if the distillate will ignite or not. A “+” sign was used to signify flammability and “-“ sign is used otherwise. The results were tabulated and a graph was constructed to determine the relationship between temperature and the volume of the distillate.
The percent ethanol was computed using the formula :
In addition, the percent loss was computed using the formula: 10
Organic Chemistry Laboratory Formal Report
References Chang, R. General Chemistry; Random House: New York, 1986. Hengstebeck, R.J. Distillation: Principles and Design Procedures; Chapman and Hall: London, New York, 1964. 11
Organic Chemistry Laboratory Formal Report Kister, H.Z. Distillation Design; McGraw-Hill: New York, 1992. Klein, D.R. Organic Chemistry; Wiley: Hoboken, N.J., 2012. Lands, W.E. The Americal Journal of Clinical Nutrition. 1995, 62, 1101S-1106S. National Health and Medical Research Council (NHMRC). Australian Guidelines to Reduce Health Risks from Drinking Alcohol; Australia, 2009. Palleros, D.R. Experimental Organic Chemistry; Wiley: New York, 2000. Pasto, D.J. Experiments and Techniques in Organic Chemistry; Prentice-Hall: Englewood Cliffs, N.J., 1998. Prado-Ramirez, R. International Journal of Food Science and Technology. 2005, 40, 701-708. Winkle, M. Distillation; McGraw-Hill: New York, 1967. http://chemistry.about.com/cs/5/f/bldistillation.htm (retrieved on Dec 16, 2012)
http://www.chem.umass.edu/~samal/269/distill.pdf (retrieved on Dec 16, 2012)
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