How aspirin is made
Willow bark started aspirin, but the factory version starts from phenol and carbon dioxide.
- stations
- 7
- things upstream
- 38
- raw sources
- 12
- steps from the ground
- 7
The short version
Aspirin starts as salicylic acid, a molecule once extracted from willow bark and now made from petroleum-derived chemicals. In a closed reactor it is combined with an acetyl-donating chemical, then crystallized, washed and dried. The pure white powder is blended with a starch binder, pressed into tablets and coated or packed in blister strips.
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Build the salicylic acid
In the Kolbe-Schmitt route, phenol from petrochemicals reacts with a strong base and carbon dioxide gas. Acid then releases salicylic acid from the salt.
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Acetylate in glass-lined vessels
Salicylic acid meets acetic anhydride in glass-lined vessels, which attaches an acetyl group. Acetic acid comes off as a byproduct.
Goes in -
Crystallize the powder
The liquid is pumped to a crystallizer and cooled. Filtering removes the acetic acid and solvent, which are recycled.
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Wash and dry
The crystals are washed, filtered and dried into the pure active powder.
Goes in -
Blend with excipients
A tablet plant weighs each ingredient, sizes it, and tumbles it with binder in a blender until the mix is uniform. Direct compression or a granulating step gets it flowing freely.
Goes in -
Press the tablets
A rotary press overfills its dies with powder, squeezes it between punches, and scrapes each ejected tablet away. Testers check hardness, thickness and how fast it falls apart.
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Coat and pack
Some tablets go through a coating pan, sometimes with an enteric coat. Blister or strip machines then seal them in foil, or they are counted into bottles.
Goes in
Worth repeating
- Salicin from willow bark has been used for its health effects for at least 2,400 years.
- Felix Hoffmann, or perhaps Arthur Eichengrün, of Bayer was the first to make acetylsalicylic acid in a pure, stable form in 1897.
- An estimated 40,000 tonnes of aspirin are consumed worldwide each year.
Back to the ground
Follow every input upstream and aspirin starts as these 12 raw sources.
Everything it is made of See it on the map
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Keep walking
Sources
- Procurement Resource: Aspirin production from salicylic acid via acetylation
- Pharmapproach: Tablet manufacturing steps
- Tableting
- The Science Snail: Organic synthesis of aspirin from benzene
- Aspirin
- Salicylic acid
Cite this page: "How aspirin is made." Assembly Line, 2026-11-03. https://assemblyline.org/make/aspirin