[Babcock_Hall]

I am helping a student with a synthesis, but I have very little experience in this particular area.  The protocol indicates that carbon was used prior to recrystallization from methanol.  Removing the carbon seems difficult for the same reasons that any hot filtration can be challenging.  If you use gravity filtration, as the solution cools it will crystallize.  I suggested using a stemless funnel and fast paper would minimize the time.  I have read that some people use Celite to help filter away the carbon.  I have often used Celite on a sintered glass funnel to remove paraformaldehyde, but I always did so at reduced pressure.  If we use reduced pressure with hot methanol, I am worried about violent bubbling taking place.  Which alternative (gravity or reduced pressure) is better?  Are there any other tricks or tips?

I can think of one idea, but it is somewhat time-intensive.  In theory one could dissolve a product in a volatile solvent in which it is highly soluble, add carbon, remove carbon by some form of filtration, remove solvent, then perform the recrystallization in a different solvent.  However, that is surely the long way around.

EDT
http://www.pitt.edu/~bandik/organicweb/decolorcarbon.html
This site suggests keeping the gravity filtration hot by use of a steam bath.

[orgopete]

I can say I used to use the celite vacuum filtration. I used extra solvent so I wouldn't get precipitation during the cooling of vacuum filtration. Evaporate (or add water) to approach saturation again. If amorphous precipitate, repeat charcoal.

Strategy two, not a fan. Charcoal-methanol absorbs/removes the least polar materials. If you use a non-polar solvent, charcoal will be less effective (ineffective?). If your impurity runs faster than your product, the charcoal-methanol. If slower, then silica-methylene chloride. Use similar treatments.