Step 2 Dissolution of the Compound
The solid to be crystallized is placed in a test tube. The solvent (the better solvent of the pair if two solvents) is added to the test tube one drop at a time. A wooden splint or boiling chip is placed in the test tube to keep the solvent from overheating (becoming superheated). Air trapped within the wooden splint or boiling chip bubbles to the top of the liquid, causing the solution to boil evenly instead of all at once. When a superheated solution boils, it frequently results in a violent action called bumping; some of the solution might be lost. The boiling stick keeps the solution from bumping. Boiling chips work in a like manner, releasing air from within the pores of the porous chip. A boiling chip is more difficult to remove than is a stick, so a boiling stick is preferable. The solvent will be added to the test tube while the test tube is being heated on a sand bath. A sand bath (metal heating mantle filled with sand) is always used with a rheostat to control the temperature. A sand bath is never plugged directly into an electrical outlet. Enough solvent will be added to the solid to dissolve the solid, whereas, the insoluble material, charcoal in this experiment, will not dissolve.