Recrystallization

Introduction

Goal:

The goal of this experiment was to purify the solid compounds of acetanilide and benzoic acid by recovering the substances as pure crystals by use of a single or mixed solvent. We heated the solvent to a boil because our compounds would disassociate better in hot rather than cold, which means a more abundant crystal outcome was produced as the compounds became insoluble in the cooling solvent.

Significance:

A solid compound is composed of pure and impure substances. crystallization works to obtain the pure substance from the impurities by using a crystallization method. As the solution of solvent and solute was heated, the solute broke down into the solvent. The pure substance and the impure substances have different shapes, therefore, as the solution slowly cools the pure substances start to crystallize; the impure substance does not separate from the solvent.

Theory:

A compound placed in a solution will break down as the solution is boiled. If let to cool down slowly, the pure and impure substances from the solute will begin the separate. The pure substance will crystallize as the impurities remain soluble in the solvent. If the pure substance does not start to crystallize during the slow cooling process, seeding is the next option. Seeding is the act of placing a small amount of already pure crystals into the still mixed solution. The seeded crystals help to promote the still soluble crystals to form. As crystals form, they form in a certain geometric shape that impurities are not able to form on, but the pure substance is; hence why seeding is an option when the pure substances do not separate from the impure.