In the crystallizing step, what can negatively affect the percent recovery?

Crystallizing at room temperature can negatively affect the percent recovery because the solubility of the compound in the solvent is often higher at an elevated temperature, meaning that not all of the compound may crystallize out at room temperature. When cooling a saturated solution slowly, the decreased temperature leads to lower solubility, allowing more of the desired compound to precipitate as crystals. If crystallization occurs at room temperature instead of a cooler temperature, the likelihood of retaining more product upon cooling is significantly diminished, ultimately resulting in lower recovery.

Cooling the solution more rapidly can sometimes facilitate quicker crystallization, ideally producing larger and purer crystals that can be easily collected and washed. Placing the solution in an ice bath after initial cooling usually helps to promote further crystallization without adversely affecting recovery, assuming the initial cooling occurs appropriately.