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Aspirin Lab Procedures

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					                                             Lab: Aspirin Synthesis
                                                  Chemistry I

Warning: This experiment will use three of the top six most dangerous chemicals that we keep in stock.    For
this reason, you will not be allowed in the lab for ANY amount of time without your
goggles. There will be no warnings. The first time that I have to tell you to put goggles on, you will be
dismissed from lab and will have to stay with me after school to make it up. If you spill the contents of your
test tube or beaker on you, wash immediately and let me know.

Day 1: The Synthesis (Making) of Aspirin
   1. One partner will set up a water bath. You will need a ring stand, wire gauze, two iron rings, a
       clamp to attach a test tube to the ring stand and a 600 ml beaker. Fill the beaker at least 3/4s full
       of water from the faucet. Begin heating the water immediately with a hot (blue) flame. Obtain a
       thermometer. When you are ready to use the thermometer, never rest it on the bottom of the
       beaker. This will measure the temperature of the glass, not the water.
   2. The second partner should obtain a large test tube (not the ones in your drawer). Using the
       weigh paper and balance, weigh out 2.00 g of salicylic acid powder and add this to the test tube.
       Bring your test tube and your stirring rod to the fume hood. Your teacher or one of the lab
       assistants will add 4 mL of acetic anhydride and 20 mL of acetic acid. Insert the stirring rod and
       stir until this dissolves. From this point on, DO NOT remove the stirring rod until the end of the
       lab. Once the powder dissolves, bring the test tube back to the fume hood where we will add 5
       drops of sulfuric acid. The sulfuric acid serves as a catalyst. Without it, you will not produce
       aspirin crystals. Stir again and clamp the test tube (w/stirring rod still in!) in the hot water bath.
       Try to set it up so that the water level in the beaker is as high or higher then the liquid level in the
       test tube.
   3. The partner in charge of the hot water bath needs to keep a conscious watch on the
       temperature. Ideally, you would like a temperature range of 84-86 degrees C. Once the
       temperature first gets to 85 degrees, begin timing 20 minutes. When the temperature gets to 87
       degrees, take the flame away. When it drops back down to 82 degrees, put it back. You will
       have to do this back and forth several times. It is extremely important that you do not let the
       temperature get above 90 degrees. The aspirin will decompose at that temperature.
   4. The partner in charge of the test tube should stir the mixture once every minute or so,
       remembering to keep the stirring rod in the test tube.
   5. Near the end of your heating time, one partner should get out a 250 mL beaker and use a
       marking pen or sticker to put your initials on it. Place approximately 30 mL of ice cold distilled
       water in the beaker (use the graduations on the side of the beaker to estimate).
   6. At the end of the 20 minutes, one partner should remove the test tube using a test tube clamp
       and cool it by running cold water from the sink over the end of the test tube until it is
       comfortable to the touch. Then, add the reaction mixture to the beaker. Transfer the stirring
       rod to the beaker. Rinse the test tube out with bursts of water from the ice cold wash bottles.
       Add this to your beaker.
   7. One partner should bring the beaker to the bucket of cold ice. Stir the mixture for five minutes.
       As the aspirin crystals form, the mixture will begin to get cloudy. If crystallization does not seem
       to be taking place, scratch the inner wall of the beaker with the stirring rod. You can also add an
       ice chip to the beaker. Rinse the stirring rod off so that the drips fall into the beaker.
   8. The other partner should be cleaning up the lab area, washing the large test tube and taking
       down your water bath if told to do so.
                                           Lab: Aspirin Synthesis
                                                Chemistry I

Day 2: Obtaining and Purifying your Aspirin Product
   1. Your aspirin will contain some amounts of unreacted acid. Therefore, the product and the liquid
       are still considered to be dangerous.
   2. Obtain a large filter paper. Weigh it and record its mass on your report sheet. Fold the paper in
       a cone. Using your ring stand and a small iron ring, place a clay triangle and funnel over the ring.
       Use a marking pen or a sticker to put your initials on the funnel. Put a large (250 mL or bigger)
       beaker beneath it. The bottom tip of the funnel should go just below the top of the beaker.
   3. Use water from the ice cold wash bottles to adhere the filter paper to the inside of the funnel.
       Make sure that the water is appropriately draining into the beaker.
   4. Slowly and carefully pour your reaction mixture into the beaker. Do not allow the liquid level to
       rise above the filter paper or you will lose product. Try to pour the liquid first, which will drain
       easier. Once the funnel is half emptied, pour more. In the end, pour the aspirin crystals. Use a
       cold wash bottle to rinse the remaining crystals of aspirin into the funnel.
   5. Rinse the product at least three times with ice cold water. Try to use the stream of water like a
       stirring rod, to churn up the aspirin crystals. This helps to rid it of any unreacted acid.
   6. Once the funnel begins to slow its drips, change the drain beaker out. Pour that liquid down the
       sink with plenty of water. The “vinegar” smell will start to disappear!
   7. Clean up your lab station, making sure all of your glass wear is clean and that everything is in
       order.

Day 3: Drying your Aspirin
   1. Obtain a large watch glass. Using a marking pen or a sticker, label it with your initials.
   2. Carefully pry the filter paper/aspirin out of the funnel and lay it on the watch glass. Open it up so
       that it will dry quicker. Put your watch glass on the “ledge” or in the fume hood – or wherever
       your teacher tells you!
   3. Wash and return your funnel and beaker.
                                            Lab: Aspirin Synthesis
                                                 Chemistry I

Day 4: Aspirin Testing/Comparisons

To begin: Obtain your aspirin product from your teacher at the fume hood. Using a piece of weighing
paper (tare the balance once weigh paper is on the scale), obtain the weight of the filter paper and
aspirin. Record this number on your report sheet. Then, get a small beaker and obtain about 50 mLs of
distilled water. You will also need a disposable dropper.

You will now test your aspirin and compare it with salicylic acid, regular commercial aspirin, expired
commercial aspirin and headache powder.

Iron (III) Chloride test:
    1. This test will show the presence of unreacted salicylic acid.
    2. Set up six test tubes. Add 20 drops of distilled water (fill a small beaker from the plastic
         container and a disposable dropper from the white box – both are on the demo table) to each
         test tube.
    3. In test tube 1, add a few crystals of salicylic acid. In test tube 2, add a few crystals of regular
         commercial aspirin. In #3, add expired commercial aspirin. #4, add headache powder. Test tube
         #5 is your aspirin product. Test tube #6 is a control (it will only have water), for comparison sake.
    4. To each test tube add one drop of iron (III) chloride, including the control (#6). Shake the test
         tubes slightly and record the colors produced on your report sheet.
    5. Which tubes show signs of salicylic acid? Well, compare them to the test tube (#1) that actually
         is 100% salicylic acid! If the test tubes have any hint of the color produced in #1, then it has
         some salicylic acid in it. If it is more like #6 (your control – which you KNOW doesn’t have
         salicylic acid in it), then it is pure! Make sure to put your conclusions on your lab report page.
    6. Empty the contents of your test tubes down the sink. Wash them up and be ready to use them
         for the next set of tests. (One partner can clean the test tubes while the other sets up for the pH
         Test)

pH Test:
   1. Obtain a tube of pH paper. Notice the color charts on the sides. The lower the number, the
       more acidic it is. A pH of 7 is neutral.
   2. Remove six pieces of pH paper and lay them side by side on a paper towel. Wet each paper with
       an equal amount of drops of distilled water. Then, add a few crystals of salicylic acid to your first
       piece. In #2, add a bit of regular commercial aspirin. In #3, add some a bit of expired commercial
       aspirin. In #4, add some headache powder. On #5, put some of your aspirin product. Again,
       strip #6 will be for control purposes only.
   3. Record the colors produced and your conclusions on your report sheet.
   4. Throw your pH strips and paper towel in the trash.
                                          Lab: Aspirin Synthesis
                                               Chemistry I

Starch Test:
    1. This test will show the presence of starch.
    2. Set up your six test tubes again. Again, add 20 drops of distilled water to each test tube.
    3. In test tube 1, add a few crystals of salicylic acid. In test tube 2, add a few crystals of regular
       commercial aspirin. In #3, add expired commercial aspirin. #4, add headache powder. Test tube
       #5 is your aspirin product. Test tube #6 is a control, for comparison sake.
    4. To each test tube, add one drop of iodine solution. A blue-black color shows the presence of
       starch. Remember, test tube #6 is the control, with just water, so you KNOW that it doesn’t have
       starch in it.
    5. Record the colors produced and your conclusions on your report sheet.
    6. Empty the contents of your test tubes down the sink. Wash them up properly and store them
       back in your drawer.

To end:
   1. Have your teacher check the results of on your lab sheet.
   2. Once given her approval, throw your aspirin in the trash along with the filter paper.
   3. Wash up your watch glass or Petri dish lid and put it in the drain rack.
   4. Wash your hands.
   5. Go back in the classroom and complete your calculations for your percent yield of aspirin. Be
       sure to show your calculations.
                                            Lab: Aspirin Synthesis
                                                 Chemistry I

                                    Report Sheet – Aspirin Synthesis

Mass of salicylic acid
Mass of filter paper and aspirin crystals
Mass of filter paper
Mass of aspirin crystals
Theoretical yield of aspirin
Percent yield of aspirin
Calculations for percent yield of aspirin




Iron (III) Chloride test

Tube Number and Contents                    Observed Color             Does the color indicate that it
                                                                       contains salicylic acid?
1 – Salicylic acid
2- Commercial aspirin
3- Expired commercial aspirin
4 – Headache powder
5 – Your aspirin product
6 – Water (control)

Starch test
Tube Number and Contents                    Observed Color             Does the color indicate that it
                                                                       contains starch?
1 – Salicylic acid
2- Commercial aspirin
3- Expired commercial aspirin
4 – Headache powder
5 – Your aspirin product
6 – Water (control)

pH test
Tube Number and Contents                    pH number, determined      Using #’s 1-6, rank them in order
                                            from color on chart        of most acidic to least acidic
1 – Salicylic acid
2- Commercial aspirin
3- Expired commercial aspirin
4 – Headache powder
5 – Your aspirin product
6 – Water (control)
                                         Lab: Aspirin Synthesis
                                              Chemistry I

Post Lab Question

Analysis and Conclusions – Key questions for your lab report! Answer below the questions, using the
room given. If more room is needed, please attach as second sheet.

   1. What can be concluded about the purity of your aspirin from the iron (III) chloride test? Should
      your aspirin have salicylic acid in it? Why or why not?




   2. What can be concluded about the purity of your aspirin from the starch test? Which of the
      substances had starch in them? Why is this true? Should your aspirin have starch in it?




   3. What can be concluded about the acidity of your aspirin from the pH test? Where does the pH of
      your aspirin rank in relation to the other chemical tested?




   4. Do the results of your tests back up Felix Hoffman, Jr.’s purpose for “inventing” aspirin? Why or
      why not?




   5. Discuss the percent yield of your aspirin. What might have occurred to cause you to either lose
      some product or possibility not produce as much as you should have? The answer to this
      question would be discussed in your “sources of error” section.

				
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