The purpose of the recrystallization step is to aid in the removal of impurities in the crude product. What are the likely identities of these impurities. How does recrystallization remove these impurities? Why was it necessary to heat the potassium oxalate solution? What was the purpose of placing the solution in an ice bath?

In recrystallization it is important that the solute dissolve in the solvent at higher temperature and the solute should be insoluble in the solvent at lower temperature. It is also important that the impurities dissolves in the solvent at normal room temperature. This is the principle of recrystallization.

The likely identity of the impurities is that it has high solubility in the solvent at lower temperature.

It is necessary to heat the potassium oxalate solution because potassium oxalate will only be soluble in the solvent at higher temperature. Increase in temperature increases solubility.

Placing the solution in an ice bath will make the solution to cool. On cooling sodium oxalate will recrystallize in a purer solid because it is insoluble in the solvent at low temperature leaving behind the impurities in the solution.