The purpose of this experiment was to prepare a sample of Aspirin and measure its boiling point

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12th October 2015

Preparation of Aspirin


The purpose of this experiment was to prepare a sample of Aspirin and measure its boiling point. Reacting salicylic acid with acetic anhydride in excess with the presence of a catalyst sulphuric acid. Through a sequence of heating, filtering and recrystallizing the end product of making aspirin was positive and the measuring of its boiling point was successful. The sample was purified and the percentage yield was calculated to be 61.2% and to measure the purity of the sample the melting point was considered which came to be 122°c.


The chemical name for Aspirin is Acetylsalicylic acid. Aspirin is known to relieve pain and is an over the counter drug. Salicylic acid was first found in the bark of the willow tree, which used to be used for treating fever and a variety of illnesses. However scientists soon began to realise that the acid used to thin the stomach lining and burn throats. (Ling, 1994)

Not long after a German scientist, Felix Hoffman, derived a pain reliever that did not produce the same side effects as salicylic acid, and is credited for the finding of Aspirin. (Ling, 1994)

Uses of Aspirin

Another use of aspirin is people having to take it to thin the blood, which reduces the chance of unnecessary blood clots to form; therefore in the long term taking an aspirin everyday will prevent heart attacks and strokes in high risk patients. There is a less chance of blocked arteries causing the amount of blood flowing to decrease and thus causing cardiac arrest. (Ling, 1994) Aspirin has been becoming increasingly popular with patients that have experienced a heart attack to avoid any recurrence taking place or tissue death surrounding the cardiac muscle.

Aspirin can also be defined as a non-steroidal anti-inflammatory drug and Aspirin being one of the first to be classed as one. (Greenlaw, 2005) These are medications with analgesics that reduce fever and have anti-inflammatory effects. Aspirin, ibuprofen and naproxen are the more common NSAIDs mainly because they can be bought over the counter and no prescription is required.

Physical Properties

Aspirin appears to be generally white although at times a colourless powder. Aspirin. In addition to aspirins physical properties, it has no odour or toxic smell, however when it does come in to contact with any type of moisture it releases a smell of acetic acid (RSoC, 2014). In cold water Aspirin is insoluble but as the water heats up the solute starts to dissolve.

Melting and boiling point

The experiment melting point is approximately 135°C. (Haynes 2013)

Preparing Aspirin by reacting salicylic acid and acetic anhydride, and recording its melting point was the aim of this experiment. A sample of the salicylic acid was weighed and then a measured amount of acetic anhydride and a minimal amount of sulphuric acid was also added. The reason as to why the reaction is heated is because salicylic acid is solid at room temperature but also to form acetyl salicylic acid and acetic acid. (chemlatech)  

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In addition heat is used to initiate a reaction, provide energy for molecules to react with another. The water is added to purify the sample and wash away any excess acetic anhydride. Using vacuum filtration the sample is filtered and weighed.

The reaction taking place in the reaction is:

Balance symbol equation:

C7H6O3+C4H6O3C9H8O4+ C2H4O2

Diagram 1 shows the skeletal formula of the changes in shape that takes place in the molecules. The limiting reactant, structure of salicylic acid contains a benzene ring and a carboxylic group. It shows ...

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