Step 3 Decolorization
This step is sometimes necessary and sometimes unnecessary. It is necessary when a colored impurity must be removed from the solution. A small amount of either powdered charcoal or charcoal pellets is added to the solution. Colored impurities adhere to the charcoal and are removed with the charcoal when the solution is filtered. Charcoal pellets are preferable to powdered charcoal because pelletized carbon is easier to remove. Charcoal is used because it presents a large surface area on which the impurity can adhere. If there are no colored impurities to remove, this step can be eliminated. In our experiment, the charcoal has already been added. In this case, charcoal serves as both an impurity and as an adsorbent for any colored impurities that might be present.