Esprit Rock

Percentage yield of crystals being higher than the original percentage

Percentage yield of crystals being higher than the original percentage, indicating that the crystals may have not dried fully, causing there to be leftover water content in the crystals when being measured. This would affect the melting point determination of aspirin as the aspirin crystals would be deemed as an inaccurate sample to measure from.
To prepare aspirin, salicylic acid is reacted with an excess of acetic anhydride. A small amount of a phosphoric acid is added which acts as a catalyst to speed up the reaction. The excess acetic acid is then removed by adding water as acetic acid is very soluble while he aspirin product is not very soluble and forms a precipitate. The aspirin isolated in this step is the “crude product”. A “purified product” can be obtained through recrystallization of the crude product in hot ethanol.