Name two factors that can affect the efficiency of a recrystallization process.

The efficiency of recrystallization is significantly influenced by both the choice of solvent and the cooling rate.

The choice of solvent is crucial because it must reliably dissolve the target compound when hot but allow it to crystallize out when cool. An ideal solvent will have a high solubility for the compound at elevated temperatures and low solubility at lower temperatures, which facilitates the crystallization process. Furthermore, impurities should ideally remain dissolved in the solvent at both temperatures, allowing for a pure product to crystallize out.

The cooling rate is also an important factor; if the solution cools too quickly, smaller crystals may form, which can trap impurities and yield a product with lower purity. A slow cooling rate allows for the formation of larger crystals, which tend to be purer as they provide a more structured lattice that excludes impurities during the crystallization process.

These factors work together to optimize the yield and purity of the recrystallized substance, making them central to the effectiveness of the recrystallization technique.