Recrystallization: Decolorization

Decolorization (if necessary)

Decolorization refers to the process of removing brightly colored organic impurities from the sample mixture. The procedure is usually carried out in the solution phase after the solid product and impurities are dissolved in a suitable solvent. Before beginning this procedure it is important to know whether the observed color is really an impurity or just the natural color of the desired product. Perform decolorization only after you have determined the color is due to an impurity. ...What would happen if you decolorized a product species that by itself was quite colorful?

Decolorize your solution by using your microspatula to add a small amount of decolorizing carbon (activated charcoal) to the warm (NOT BOILING) sample solution. Activated charcoal has a great deal of surface area upon which impurity molecules will attach themselves removing thus removing these species from the solution. Later, the carbon/impurities are removed via gravity filtration.

Caution:

• Don't add activated charcoal to a solution that is near boiling. Violent foaming may result that can dangerously propel the solution out of the flask.
• Decolorizing carbon also removes product species. Don't repeat this procedure more than twice or you will seriously reduce the amount of product you hope to recover.