The first known use of aspirin was by Greek physician Hippocrates, who used powder extracted from the bark of a willow tree to treat pain and reduce fever. The bark contained salicin, a component of acetylsalicylic acid, or aspirin. Salicin was successfully isolated from willow bark in 1829. Unfortunately, aspirin irritated the stomach. In 1897, chemist Felix Hoffmann, working for Bayer, concocted a less acidic formula. On this date in 1899, Hoffman received a patent for the new, improved aspirin.

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