[tiger17]

We had to recrystalize benzoic acid, I'm having a hard time figuring out what the reaction is because we only used benzene, water, and charcoal.  This was our procedure:

1. Add 1 g impure benzoic acid + 15 mL water
2. Heat with condenser
3. Add little more water
4. Cool
5. Add a little carbon
6. Reheat
7. Hot filtration
8. Ice water bath
9. Vaccum filter

[sundberg]

The theory behind recrystallisation doesn't involve any mechanisms, it's just based on solving the compound being purified in a suitable solvent and then allowing it to cool slowly to allow reformation of crystals. This way impurities doesn't get trapped, which is the case when crystallization is instantaneous/fast.

Active charcoal also traps impurities, and is often used to remove miscolorations of compounds etc.

[tiger17]

I know, that's why I was confused.  So is there also no reaction?

[sundberg]

Not except solving of the crystals.