Recrystallization

Fold filter paper in half and crease sharply, then unfold and rotate 90 degrees. Repeat this process four times, alternating between making creases and filling in spaces between pleats, until you have a tightly pleated paper that can fit inside a funnel.

Place the crude acetylsalicylic acid material in a beaker, add a small amount of room temperature water, and heat on a hot plate while swirling until all material dissolves. This heating process releases any trapped salicylamide impurities into the solution.

Place a warm Erlenmeyer flask containing recrystallization solvent on a hot plate with a glass funnel and pleated filter paper on top. Pour the heated solution through the filter paper into the warm flask to remove any insoluble material while preventing premature crystallization.

Transfer the filtered Erlenmeyer flask to an ice bath to cool the supersaturated solution, which will promote crystal formation of the desired acetylsalicylic acid compound.

Generate nucleation sites for crystal growth by either adding a pure crystal of acetylsalicylic acid with a spatula or gently scratching the bottom of the glass vessel with a glass stir rod. This seeding process triggers crystallization and helps exclude salicylamide impurities from the growing crystals.

Once acetylsalicylic acid has completely precipitated from the cooled solution, separate the pure crystals from the remaining liquid using vacuum filtration.