Today, you will complete you aspirin synthesis (Experiment #31) by getting the mass of your synthesized acetylsalicylic acid (aspirin) and obtaining its’ melting point.  Compare this melting point to the melting point of aspirin in the MERCK Index or the CRC Handbook of Physics and Chemistry.  If your sample has a lower or a “wide range” melting point than that listed, it contains impurities.

INFORMATION About Aspirin:  Aspirin hydrolyses in vivointo salicylic acid and acetic acid.  Salicylic acid is a pain-killer (analgesic) and a fever-reducer (anti-pyretic).  Salicylic acid is too irritating to the lining of the stomach to be taken internally by itself, so it is reacted with the acetic acid (or a derivative) to prepare aspirin.  Aspirin is not, according to the F.D.A., to contain free salicylic acid.

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  • Weigh the aspirin made in the last lab period. Record this mass in your Expt. #31 lab report.
  • Get a sample for the melting point.Put it in the glass capillary. Do the melting point.
  • Put this information in your lab book under experiment 31 which you can now finish outside of class.



  • Weigh about 0.500 g of your lab made aspirin; record this mass in Table 1 below. Grind it in the mortar and pestle, determine if it smells like acetic acid (vinegar). Record this in the Observations Table (on page 3) and put the ground aspirininto a small beaker.
  • Get 2 other aspirin tablets – one of which is BRAND X (which we provide).You need to bring another aspirin tablet to test also.
  • Record how much aspirin is in each tablet (read the label).  Put this number in the 2nd row of the table below.
  • Weigh each tablet and record its’ massin the same table.
  • Grind each tablet separately, smell it and record this in the Observations Table. Then put the ground aspirin in its’ own small beaker.
  • Add about 30 mL of water to each beaker (all three of them) and stir each with its’ own stirring rod.


Aspirin Sample Name Made Aspirin

(From Expt 31.)

Brand X Other Aspirin

(You provide)

Mass of sample      
Mass of aspirin

in sample

0.325 g

(325 mg)

Percent Aspirin

in sample



  • Re-stir the samples and then touch a drop of each aspirin solution to a piece of pH paper and record its’ acidity(pH) on the Observation and Results Tables. (The number should be between 1 and 7)



Now you will perform both the Lugol’s test and then the Iron Nitrate test.  The Lugol’s test looks for the presence of starch and the Iron Nitrate test looks for salicylic acid.  You decide which to do first.

  • For each one of these tests you will need 5 test tubes. (Be sure to label them as indicated in the figure below.)
  • Measure the amount of distilled water needed for the test (3 mL) with a 10 mL graduate cylinderand put it in a test tube.
  • Fill three of the other test tubes with the aspirin solutions to the same heightas the water in the first test tube. (You don’t have to measure them with the graduate cylinder again); Onlyone aspirin sample per test tube.(See Figure below.)
  • To the last test tube,fill with your control solution (Either Starch for the Lugol’s test or Salicylic Acid for theIron Nitrate test) to the same height as the water in Test Tube #1.
  • Add the correct amount of the test reagent for the test you are doing (3 drops: for Lugol’s testor 6 drops for the Iron Nitrate test) to all five the test tubes and continue the procedure.
  • Observe what happens and record.Now, repeat this entire process (Steps 1-6)for the other test.

Water      Asp 1       Asp 2        Asp 3     Control

Blank        Your        Brand X      [Starch (Lugol’s test)

AspirinSalicylic Acid (Iron Nitrate test)]


With the Lugol’s test and the Iron Nitrate testcompleted, start the Benedict’s test to look for lactose.

  • Get the hot plate down from the shelf and put tap water in your 400 or 600 mL beaker (until about half filled) and start heating it .You will use this for a water bath for the test tubes.
  • To each of the 3 beakers of aspirin solution, (one at a time), add NaHCO3or Na2CO3solution until a drop of the solution, taken with a clean glass stirring rod, does not turnblue litmus paperpink.
  • Repeat with the other aspirin containing beakers. You now have neutralized the aspirin solutions.
  • Get 5 test tubes and label them as in the Lugol’s or Iron Nitratre test.
  • Measure the water sample needed for the Benedict’s test (3 mL) and put it in one test tube. In 3 of the other test tubes, put the same height of aspirin solutions like before.  In the last test tube put the same height of lactose solution.
  • Measure 3 mL of the Benedict’s reagent and add it to the water test tube.
  • Put the same height of Benedict’s reagent in the other 4 test tubes.
  • Stir them and then heat the test tubes in the boiling water bath for 10minutes until the lactose solution changes color.
  • Record your observations in the Observations Table..

Finally, in the Results Table  indicate if you got a positive or negative result for each test and each sample.

TABLE  2   –  OBSERVATIONS(Record the pH and colors of the solutions here)

Aspirin Sample Name Made Aspirin

(From Expt 31.)

Brand X Other Aspirin

(You provide)

Odor       None
pH       Not tested
Lugol’s test

(for Starch)

Iron Nitrate test

(for salicylic acid)

Benedict’s test

(for lactose)



TABLE  3  –  RESULTS               (Indicate whether your observations are positive or negative)

Aspirin Sample Name Made Aspirin

(From Expt 31.)

Brand X Other Aspirin

(You provide)

Lugol’s test

(for Starch)

Iron Nitrate test

(for salicylic acid)

Benedict’s test

(for lactose)




  1. Is there any difference in the amount of aspirin, per tablet, among the various brands?


  1. Is there any difference in the percentage of aspirin, per tablet, among the various brands?


  1. Which brand contained the lowest amount of aspirin? ______________________________
  2. Which brand contained the lowest percentage of aspirin? ___________________________
  3. What other substances besides aspirin were in the tablets? (answer from data from your experiment and from the labels on the aspirin bottles)? _________________________________________


  1. Do any of the tablets give a positive test with the Iron Nitrate? _______________________If yes, what possible explanation can you make. _____________________________________________________________________________


  1. How do the pH values of the samples compare?_____________________________________________________________________________


  1. Is there any difference in the pH of buffered and regular aspirin?_____________________
  2. What is the reason some individuals may take buffered aspirin? _______________________


  1. What is the risk in buying extra large bottles of aspirin? ______________________________


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