Decolorizing Carbon
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     Decolorizing carbon, also called activated charcoal, is finely divided carbon often used to decolorize a solution.  The small particles of decolorizing carbon provide a large surface area to which large colored molecules may become adsorbed.

     Since decolorizing carbon is composed of carbon exclusively, nonpolar molecules an easily adsorb to its surface.  This presents a real problem if a desired nonpolar compound is present as well as colored impurities in solution.  The desired compound may adsorb to the carbon as well as the colored compounds, thereby reducing the amount of product recovered.  Knowing the amount of decolorizing carbon to add and the circumstances to add it are, unfortunately, gained by experience.  Consult you TA as to its appropriate use.

     If decolorizing carbon is to be added to a colored, heated solution, swirl the flask briefly before added.  This will prevent the solution from boiling over unexpectedly upon addition of the decolorizing carbon.

     Add enough decolorizing carbon as necessary, stir with a glass rod or swirl the flask briskly.  

after addition of charcoal
(click on the photo for enlargement)

Quickly begin to gravity filter the solution.  The longer the decolorizing carbon remains in solution, the greater the chance of adsorbing desired compound.  Keep the flask over a heat source (e.g., steam bath) while filtering.  This will keep the desired compound dissolved in solution.

hot gravity filtration to remove decolorizing carbon
(click on the photo for enlargement)

Notice on the picture above the charcoal with impurities adsorbed to its surface is collected on the filter paper while performing gravity filtration.  The solution, now uncolored, is collected while keeping the flask over a heat source.

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Last updated: 8/24/99