Caffeine solubility Temperature differences...?

Question

The wiki says:

22 mg·mL−1 (25 °C)

180 mg·mL−1 (80 °C)

670 mg·mL−1 (100 °C)

Lets say you have 100ml of water, and you heat it to 80 degrees C, and you add 18 grams of caffeine to it, and mix it up, you have the maximum caffeine per mililitre of water.. If you cool the water too 25 degrees C, will there be excess caffeine solids forming in the water because the water can no longer hold that quantity of caffeine in the water soluable? Or is it the case that because the caffeine was disolved in water at a temperature of 80, that even when the temperature goes to 25, the caffeine is still disolved in the water? How does this work exactly?

Answer 1

This is a typical procedure of recrystallization. Upon cooing down the amount of solute (caffeine) that exceeds the solubility at the given temperature will precipitate and become an insoluble solid.

There are sometimes exceptions  and the solution holds more of the dissolved stuff than given by its original solubility. As  long as no agitation of the solution takes place (moving scratching, stirring etc.) it remains as a so called supersaturated solution.