Comparative Analysis of the Purity and Price Level of Different Aspirin Tablets

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Background information

One of the most common drug used in our society is aspirin which was one of the first drugs to come into common usage.

What is aspirin?

Aspirin is a white crystalline powder with a melting point of 135 C. The common chemical name for aspirin is acetylsalicylic acid. Its systematic name is 2-(acetyloxy) benzoic acid. The chemical buy Cialis no prescription formula of aspirin is C9H8O4 and the atoms are arranged according to the following diagram

How was it discovered?

The ancient Egyptian made used of willow bark a plan which contain salicylic acid for aches and pain.

Salicylic acid is the key ingredient of aspirin but this was only discovered around the 18century when Edward stone discovered aspirin by showing how a preparation of willow bark powdered help 50 patients of ague. It was in the year 1874 that a scientist Hermann Kolbe discover synthetic salicylic acid but this was not easy to use since a when administered could easily course nausea and vomiting to a patient and sometime even bring him to a coma. To reduce this effect a buffer was need, this came out with the introduction of what is today known as aspirin by the chemist Felix Hoffman at Bayer in the year 1890 in the form of acetylsalicylic acid

How does aspirin work?

Damaged cell usually produce and enzymes called cyclooxygenase which produce a chemical called prostaglandin which send a message to the brain that a part of the body is in pain. Aspirin act as a non-steroidal anti-inflammatory drug, it directly act on the source of the pain and prevent the production of cyclooxygenase therefor reducing pain sensation. The problem with this is that cyclooxygenase is also known for producing mucus lining of the stomach so a common or daily used of aspirin will result to stomach ulcer and also since it is a weak acid it reduce stomach ph. to solve the fall in stomach ph a buffer is usually added to aspirin tablet.

Why is aspirin buffered?

A buffering agent, such as that contained in buffered aspirin, is used to preserve the pH of the aspirin as it is introduced to the patient 39;s stomach, which is very acidic. Acetylsalicylic acid


Aspirin is one of the most common drug which is been used to solve pain problems over a countless number of different, it can also been used to reduce cancer risk and avoid heard attack. In my whole life I cannot remember of a day when I had pain problem and I was unable to find a tablet of aspirin, even when you are not searching for an aspirin tablet but for another drug your eyes will always enter in contact with an aspirin table so I slowly made the deduction that it was the most abundance and common drug in the world. My confusion with aspirin appeared when a day I took two different tablet of aspirin, I read what was written on the two and I did not understood the logic behind it. It was clearly written that the two were aspirin tablet but the brand name was different and they also had different price but, finally I decided to use the one with the greatest price following the logic that it cost more so has more effect but I could not bring exclude the fact that I have been using the drug for years and I must already have tested a great variety of aspirin tablet from different brand without knowing but I have never seen any different so my question was why does they have different price? To answer this question I came out with the idea that since aspirin also known as acetylsalicylic acid is the main component of all the tablet must come from the aspirin concentration in each table. My experiment will consist of a titration of different aspirin tablets to find out the concentration of aspirin in each and find out if the price different is justify.

With the use of sodium hydroxide and ethanol I will compare the purity and price level of of different aspirin tablets.

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Reaction with sodium hydroxide

This is an acid-base reaction in which the acetylsalicylic acid reacts with the base sodium hydroxide to produce the salt sodium acetylsalicylate and water (acid + base → salt + water). ... This is called the “end point” of the reaction. If one continues adding NaOH after the end point, the solution will turn dark red.

  • C₉H₈O₄+NaOH=C9H7O4Na
  • C₉H₈O₄+NaOH=C9H7O4Na+H2O

Why is ethanol used in the titration?

Ethanol is used in the titration to dissolve aspirin. It is then titrated against sodium hydroxide (base) using phenolphthalein as indicator. Ethanol has a hydrophobic carbon chain. In this sense, water can only dissolve the carboxylic acid and polar portion of aspirin but the methyl ester may not be properly dissolved. so as ethanol is used to speed up the reaction and to better dissolve the aspirin. Acetylsalicylic acid is slightly soluble in water, with a limit of solubility reported as approximately 3 mg/ml at 25 Deg C.It is also soluble in ethanol at 50 mg/ml. so it is more soluble in ethanol than in water.


Variables independent Initial and final burets reading dependent Purity level Depend on the mass of aspirin present and mass the tablet. control Mole of NaOH 0.1mole AIM: measuring the concentration of aspirin in tablet of different brand


  • 0.100 M of NaoH, Ethyl alcohol, various aspirin tablets,150 ml flask, a burets ,mortar and pestle phenolphthalein indicator and goggles


  • Find the mass of different aspirin tablet, then grind each of them in a fine powder using mortar and pestle.
  • Tare a piece of weighing paper on the balance. Carefully transfer as much powdered sample to the paper and find the mass.
  • Place the powdered sample in a 150ml beaker.
  • Add a 10.0ml portion of ethyl alcohol to the beaker and stir.
  • Add 25.0ml of water to the beaker.

Put 3 drops of the phenolphthalein indicator in your flask. Put a magnetic stir bar in your flask and place the flask on the center of the stir plate

The burette is filled with 0.100M of NaOH and record the initial volume on the burette. There must be no bubbles apparent in the burette.

Begin titrating. Add the NaOH in 1.0ml increment, making note of the color change occurrence. Continue adding base 5.0ml and past the equivalent point, this is when the solution turn pink due to the phenolphthalein.

Repeat the step for all aspirin tablet.

Data and calculation

  • Below is a diagram of the chemical equation that show the reaction between aspirin and sodium hydroxide.

First tablet

  1. Aspirin brands Mass in grams First trial cm3
  2. Second trial cm3
  3. Third trial cm3
  4. Average in cm3 price
  5. Aspirin cardio 5.6 5.1 5.4 5.4 5.3 6300fcfa
  6. Mass of a tablet= 5.2 g
  7. Concentration of sodium hydroxide= 0.100mol/dm3
  8. Volume of sodium hydroxide needed to neutralize it=5.3 cm3
  9. Number of mole of NaOH (5.3〖cm〗^3)/1000×0.100mol/〖dm〗^3 =0.00053moles
  10. If 1 mole of aspirin neutralize 1 mole of NaOH
  11. Aspirin has a chemical formulae of C9H8O4 and a relative molecular mass of 180.2 grams.
  12. So 0.00053 mole of aspirin neutralize 0.00053 mole of NaOH 1 mole of aspirin has a mass of 180.2
  13. A pure tablet will have 5.6/180.2= 0.03108 moles
  14. The Purity of aspirin is obtain by (Actual moles)/( possible moles )→0.00053/( 0.03108)=0.01705
  15. To change this answer into percentage, multiply it by 100. This will give 1.705%.
  16. That is 1.705% pure, this mean that this tablet is compose at only 1.705% of aspirin.

Second tablet

  1. Aspirin brands Mass in grams First trial cm3
  2. Second trial cm3
  3. Third trial cm3 average in cm3 price 1.03 5.7 5.5 5.3 5.5 850fcfa
  4. Mole of NaOH used is (5.5×0.100)/1000=0.00055mole
  5. Possible mass 1.03/180.2=0.00572mole
  6. Purity of aspirin 0.00055/0.00572=0.0962
  7. Multiply it by 100 to change it to percentage
  8. That is 9.62% purity

Third tablet

  1. Aspirin brands Mass in grams First trial cm3
  2. Second trial cm3
  3. Third trial cm3 Average in cm3 price 4.64 5.3 5.4 5.6 5.4 5200fcfa
  4. Mole of NaOH used is (5.4×0.100)/1000=0.00054mole
  5. Possible mass 4.64/180.2=0.02576mole
  6. Purity of aspirin 0.00054/0.02579=0.0209
  7. Multiply it by 100 to change it to percentage
  8. That is 2.09% pure


  • Quantity or mass of aspirin found in each table (%purity)/100×mass of table
  • For the first tablet=1.71/100×5.6grams=0.957grams
  • Aspirin brand % purity Mass of aspirin present Price in fcfa
  • First tablet 1.71 95.7mg 6300
  • Second tablet 9.61 99mg 950
  • Third tablet 2.09 97mg 5200
  • The uncertainty of the values is obtain with the formula range/2
  • Uncertainty of first titration=(5.4-5.1)/2=0.15
  • Uncertainty of second titration=(5.7-5.3)/2=0.2
  • Uncertainty of third titration=(5.6-5.3)/2=0.15
  • Uncertainty of the experiment (prescribe mass-mass obtain in experiment)/(prescribe mass)×100
  • For the first titration (100-95.7)/100*100=4.3%
  • For the second titration, the uncertainty is 1%
  • For the third titration, the uncertainty is 3%


They all have about 100mg of aspirin in them but they have different purity level due to different in mass. The tablet with the highest price has the lowest purity level and the one with the lowest price has the highest purity level. Therefore aspirin purity and price are inversely proportional. This is because has side effect on the stomach so usually aspirin tablet are coated or buffered. Buffered aspirin, combines an antacid such as calcium carbonate (found in Tums) or aluminum hydroxide (found in Maalox) with the higher the buffer solution the lower the effect of aspirin on the stomach therefor one tablet of 1.7% purity has less side effect than one with 9% despite they contain about 100mg of aspirin.


  1. Essay on Determination of Asa Content of Aspirin - 2438 Words. (n.d.). Retrieved from
  2. Acetylsalicylic Acid. (n.d.). Retrieved from
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Comparative Analysis of the Purity and Price Level of Different Aspirin Tablets. (2022, September 27). Edubirdie. Retrieved April 17, 2024, from
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