A second crop of caffeine may form in the filtrate as the solvent evaporates. This second crop can also be collected by vacuum filtration but keep it separate from the first crop. The sublimation will be performed as described by your instructor. You will not take a mp of the purified caffeine which would require a sealed capillary to prevent sublimation near the melting point. Save the purified caffeine in a sealed vial.
Caffeine is a base which can react with acids to form salts.
A well characterized salt of caffeine is caffeine salicylate formed by using salicylic acid. This derivative of caffeine has an accurate melting point. Later this semester, you will be required to make solid derivatives of other compounds. Preparation of Caffeine Salicylate . Erlenmeyer flask by warming on a steam bath.