Question

Compare and contrast the techniques (Evaporation, Filtration, Crystallization). When is each technique appropriate? What are the advantages vs disadvantages? Why was the vanillin exposed to two different techniques? Could we have isolated the vanillin using a different technique? Why or why not?

Answer 1

Evaporation is used when the both the solvent and the solute are not affected by the high temperature. It cannot be used where the solvent and/or solute start to react or decompose or polymerize due to the temperature.

Filteration is used when the solute particles are larger and can be separated by such mechanisms. It is a normal temperature process but highly dependent on the particle size.

Crystallization is used when one is interested in extracting solute particles from the solution. It is dependent on the solubility as a function of temperature. It may require seeding sometimes. But it gives very controlled separation.

The vanillin was first crystallized and then filtered. Evaporation was not a very good idea as it could have damaged the molecule. However, if we would have used low pressure evaporation, then it could have been separated using evaporation only.