Producing Aspirin By Vacuum Filtration

Authors Avatar by serhad1234hotmailcouk (student)

Making Aspirin

Aim: to be able to make aspirin


  • Vacuum Filtration – Buchner funnel and flask
  • Balance
  • Air Condenser
  • Conical Flask
  • Beaker
  • Measuring Cylinder
  • Spatula
  • Petri Dish
  • Hot water bath – approx. 60oC
  • Hydroxybenzoic Acid
  • Ethanoic Anhydride
  • Sulphuric Acid
  • Distilled Water


  • Collect all the equipment, using a measuring balance weigh out 5.0g of 2-hydrobenzoic acid in a conical flask. Then add 7cm3 of ethanoic acid anhydride and also add three drops of concentrated sulphuric acid.
  • At the top of the conical flask fit the air condenser and mix together the reagents and then add to a water bath with a temperature between 50- 60 °C for 15 minutes.
  • After you have taken the conical flask out of the water bath then run it under cold water, remember not to remove the air condenser.
  • Next add 75cm3 of distilled water, and then using a glass rod stir well.
  • Then using a separating funnel adds filter paper to the top of the vacuum filter and then pours the solution into the Buchner funnel. Release the tap so water allows the filtration to process quickly. Then collect the solids which have been separated in  the vacuum filtration
  • Re-crystallise by transferring the crude product to 100cm3 flask and add in 15cm3 of ethanol, alongside 45cm3 of distilled water. Then fit the air condenser and place the conical flask into the water bath  until the crude has dissolved
  • Allow the solution to cool and then collect the product by vacuum filtration.
  • Finally dry the product at room temperature.
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Vacuum filtration:

Vacuum filtration is a technique used for separating a solid product from a solvent, or liquid reaction mixture, the mixture of solid and solvent is poured through a filter paper in a Buchner funnel, the solid is trapped in the filter paper and the liquid is poured through into a flask below by a vacuum. A filter is used to separate the solid from liquid by a vacuum pump to force the liquid through the filter. This is why vacuum filtration is used to obtain recrystallized solids such as aspirin. The liquid in the solution will ...

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