Question

In an experiment where students are isolating Acetylsaliclic Acid (ASA) from Aspirin tablets,

would recrystallization work if you had 5 grams of an impurity contaminating 1 gram of your desired product and both were soluble in the recrystallization solvent at its boiling point and insoluble at room temperature? Why or why not?

Answer 1

Recrystallization technique is used to separate desired compound from impurities when the concentration of impurities is minimal. In the present case, the impurity to acetylsalicylic acid (ASA) is 5 : 1, which is very high. In such case, even though we would be able to remove some part of impurity initially. The final crystals would be contaminated with impurity as the concentration of impurity and compound would be almost the same. Thus this method is not suitable for the separation.