The Separation of the Components of a Mixture by 2i48203

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									             Experiment #2: Steam Distillation of Essential Oils


Background:
   Distillation consists of heating a liquid until it vaporizes, and then condensing the
vapor and collecting it in a separate container. Distillation is used to separate mixtures
of liquids that either have different boiling points, or that have one component that
does not distill. There are many types of distillation, each of which has a distinct
purpose. Steam distillation is used to isolate volatile substances that have high boiling
points. When two immiscible liquids are distilled together, the amounts of each
component in the distillate are constant. Also, the boiling point of the mixture is lower
than that of either of the individual components. This is because the components do not
have compatible intermolecular forces, and so the component in lesser concentration
will form “bubbles”, like oil droplets in water, weakening the overall intermolecular
forces in the mixture, and thus lowering the boiling point. This process allows high-
boiling compounds, which can decompose before they boil if heated alone, to be
distilled at temperatures below 100C.
   Steam distillation is one of the methods used for obtaining essential oils from various
substances. Essential oils are used widely in foods, fragrances and medicines. These
oils consist primarily of fragrant compounds that are most often aromatic compounds
and/or aldehydes, phenols, esters and alkenes. Because one of the components in
steam distillation is water, the boiling point of the mixture should be less than 100C. In
this experiment you will isolate the essential oil from one of the following sources:
cloves, cinnamon, lemon peel or orange peel. Typically, cloves contain 10-15% euganol
and cinnamon contains around 5% cinnamaldehyde (not sure how much limonine is
typically in citrus peel). Cloves will be provided in the lab, but you must bring your
own if you want to do one of the other three. Cinnamon sticks are best (not powder) if
you choose that one. You will isolate your oil from the distillate using a method called
extraction. Extraction consists of partitioning the components of a mixture between two
immiscible liquids in order to separate the components. The structures of the primary
components of each of these essential oils are shown below:
          OH
                                                     O
                  O
                      CH3
                                                         H




            Euganol                   Cinnamaldeh yde                 Limo nine
         (from cloves)                (From cinnamon)             (from le mons and
                                                                      oranges)
Materials:
   5 g cloves (or cinnamon, lemon peel or orange peel from home), 100 mL round-
bottom flask, water condenser, distillation head, thermometer adapter, vacuum adapter,
thermometer, heating mantle, power supply, 50 mL graduated cylinder, 2 beakers, 2
erlenmeyer flasks, clamps for glassware, Keck clamps (blue plastic), and mortar and
pestle (or scissors), 125 mL separatory funnel and watch glass

Safety Precautions:
   Dichloromethane is not flammable, nor is it considered carcinogenic, but it can cause
liver damage if ingested, or with repeated inhalation or skin exposures. It should be
used in the fume hoods (inhalation of vapors can cause nausea or drowsiness). Avoid
spills; it can also pass through both latex and nitrile gloves.

Procedures:
1. Prepare the spice. Weigh out approximately 5 grams of your spice and record the
mass. If you are using cinnamon sticks you should break them up into small pieces and
grind them up a bit with a mortar and pestle. If you are using citrus peels you should
cut them up with scissors. If you are using cloves you should grind them up a bit with
a mortar and pestle.

2. Set the 100 mL round-bottom flask in the heating mantle and clamp it to a ringstand.
Place two boiling chips in the flask; add your spice to the flask; add about 50 mL of
distilled water.

3. Assemble the rest of the distillation apparatus (see figure on page 4, your set-up will
be similar), connecting the pieces with the clips provided. Make sure the entire
thermometer bulb is below the sidearm of the distillation head. Water should go in on
the lower side of the condenser and exit on the upper side. You may want to clamp the
loose hose end over the sink so it doesn’t spray the lab. Place the Erlenmeyer flask
below the end of the condenser to receive the condensed liquid.
4. Heat the flask with the heating mantle so that the liquid boils gently. Record the
temperature when the first drop comes over. Try to obtain a steady rate of distillation,
around 1 drop per 2-3 seconds. If you approach the boiling point too quickly, or boil
too hard, you may get frothing and or bumping, which can contaminate your distillate.
Every so often transfer the distillate from the Erlenmeyer to a graduated cylinder.
Continue distilling until you have collected about 30 mL of distillate. Record the
temperature again at the end of collection.

5. Remove the flask from the heat and turn off the heating mantle. Let the apparatus
cool before taking it apart. The small clamps go back in the box on the cart. The blue
clamps for the glassware go back in their box on the cart. Dry off the thermometers and
put them back. The glassware should be rinsed with water, then placed in the dirty
glassware bin.
6. Place all of the distillate into a separatory funnel. Add 10 mL of dichloromethane,
shake, and allow the layers to separate. Collect the dichloromethane in a clean
Erlenmeyer flask (the dichloromethane will form the bottom layer). Do not collect the
middle emulsion layer. Repeat this 2 more times. On the third extraction, shake more
gently and allow more time for the emulsion to clear. Rinse the sep funnel with water
and place it in the dirty glassware bin.

7. Add a few small scoops of drying agent (sodium sulfate); add until the drying agent
no longer clumps together when swirled (should look like a snow-globe). Allow to
stand for 10-15 minutes, stirring occasionally.

8. Carefully decant the liquid into a clean, pre-weighed beaker, trying not to pour over
any of the solid. If time permits, evaporate the dichloromethane with a gentle stream of
nitrogen (or air, if nitrogen is not available) while heating to around 40C. Or, if time is
up, place a cover loosely over the beaker and leave to dry in the hood until the next
class period. When it is dry, weigh the beaker + oil and record the mass.

9. Calculate the mass of the oil and the percent by mass recovery (based on the mass of
the spice used).

Waste Disposal:
   Aqueous solutions may be diluted and flushed down the drain with plenty of water.
Allow the dichloromethane to evaporate from the drying agent and then place it in the
solid waste container. Put solid spice residues in the trash (do not wash down the sink
as they may cause a clog). Place any extra dichloromethane into the organic waste
container.

Pre-Lab:
  Prepare your notebook as described in the lab notebook handout. Include: name,
partner’s name, title of experiment, date, purpose, structure of compound to be isolated
(based on which spice you choose), procedures (bulleted list), sketches of glassware set-
ups, separation scheme (flow chart) and data (make spaces to record masses, volumes
and temperatures). Leave spaces for observations.

Report:
1. In your notebook, write a brief discussion of the experiment. In this section you
should summarize your results (mass of oil obtained and % recovery), note any
interesting observations (odor and color of oil) and make any possible conclusions
about the experiment (successful vs. unsuccessful and reasons why). Be sure to
compare your results to the expected results.

2. Answer the post-lab questions.

3. Make a copy of your lab notebook pages (do not tear out the originals) and attach the
question sheet with your answers. Staple all pages and turn it in.
Name ____________________________________


Post-Lab Questions:

1. Why does the distillate that you collect initially appear cloudy (hint, see Ch. 9)?




2. Why does the dichloromethane form the bottom layer during the extraction step?




3. What is a drying agent and how does it work (hint, see Ch. 9)?
4. Would you expect to get all of the essential oil out of your spice using the procedures
in this lab? Why or why not?

								
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