When it comes to recrystallizing aspirin, the best solvent is typically a combination of ethanol and water. Aspirin, or acetylsalicylic acid, is fairly soluble in organic solvents and slightly soluble in water, which makes this combination particularly useful.
A key factor in choosing a solvent is the solubility of the compound at different temperatures. Ideally, you want a solvent that dissolves the compound well when hot but not when cold. Ethanol provides good solubility for aspirin when warm, while the addition of water can reduce the solubility when the solution cools down.
Using this mixture allows for a more controlled cooling process. As the solution cools, the aspirin will start to crystallize out of the solution, effectively purifying the compound from impurities that remain dissolved. Furthermore, this combination can help achieve a cleaner product due to the different solubility profiles.
In summary, using a mixture of ethanol and water for recrystallizing aspirin balances solubility properties and purification efficiency, making it an effective choice for this process.