CHM 2210L Chapter Notes - Chapter 4: Xue Xu, Naphthalene, Pasteur Pipette
Document Summary
Recrystallization is a technique used by chemists to purify substances that crystalize upon the removal of their solvents. Materials are dissolved into a hot solvent and the solute precipitates as the solution cools. As the precipitation occurs, a perfect crystal lattice excluding impurities forms as impurities are too dilute to precipitate along with the desired substance. 1 so long as the impure substance has a higher concentration, it will crystallize prior to the crystallization of impurities as the solubility decreases with decreasing temperature. The process works best when the quantity of impurities is small and rapid changes in solubility coincide with changes in temperature. Slower cooling will allow for the formation of larger crystals. Though the process can be effective at obtaining pure samples, the procedure takes a large amount of time. 2. The following generalized procedures summarize the process of recrystallization from an experimental standpoint. As described in the lab manual, recrystallization can be described in seven steps3:
