Vernier Software and Technology
Vernier Software & Technology

Recrystallization of Benzoic Acid and Aspirin


A fundamental purification technique for organic solids is recrystallization, which uses the different solubility of solutes in a solvent. Generally, compounds isolated from organic reactions are impure and require purification to obtain the desired clean product. Recrystallization is a purification process because the slowly growing crystals incorporate only those same molecules that fit correctly into the crystal lattice. The impurities that do not fit into the crystal lattice remain in solution.

The solubility of the compound in the recrystallization solvent is important. In general, a minimal amount of hot solvent would completely dissolve the compound to be purified. Upon cooling, the impurities will remain in solution as the desired compound crystallizes. A suitable recrystallization solvent should also be somewhat volatile in order to be easily removed from the purified crystals.

If the cooling process is allowed to proceed slowly, nearly pure crystals of the compound will form. If the solution is cooled too quickly, the impurities will precipitate out of the solution along with the desired product. Once crystallized, the solid can be collected by vacuum filtration, washed with cold solvent, and dried. The purity of the recovered solid can be analyzed by determining the melting temperature.


In this experiment, you will

  • Recrystallize a sample of contaminated benzoic acid.
  • Test the solubility of acetylsalicylic acid.
  • Recrystallize acetylsalicylic acid from aspirin.
  • Characterize the compounds by melting temperature analysis.

Sensors and Equipment

This experiment features the following Vernier sensors and equipment.

Additional Requirements

You may also need an interface and software for data collection. What do I need for data collection?

Organic Chemistry with Vernier

See other experiments from the lab book.

1Determining Melting Temperature
2Recrystallization of Benzoic Acid and Aspirin
3Determination of a Boiling Point: Simple and Fractional Distillation
4Identifying an Unknown Analgesic by Melting Temperature and Thin-Layer Chromatography
5Separation of Organic Compounds by Acid-Base Extraction Techniques
6Understanding Polarimetry
7Identification of Organic Unknowns Using Polarimetry
8Investigating Gas Chromatography
9Fractional Distillation of Esters
10Understanding Intermolecular Forces Using a Gas Chromatograph: Enthalpy of Vaporization
11Investigating Thermodynamic Relationships of Substituted Hydrocarbons
12Extraction of Spinach Pigments and Analysis by Electronic Absorption Spectroscopy
13SN1: Synthesis of t-butyl chloride
14SN2: Synthesis of 1-bromobutane
15Observing the Reaction Kinetics of Sucrose with Polarimetry
16The Synthesis and Analysis of Aspirin
17Isolation and Epoxidation of a Natural Product: Limonene
18Synthesizing Ethyl Acetate by Fisher Esterification
19Synthesis of Dibenzalacetone by Aldol Condensation
20The Diels-Alder Reaction of Anthracene with Maleic Anhydride
21Friedel-Crafts Acylation of Ferrocene
22Grignard Formation of Crystal Violet
23Synthesis of Fluorescein
24Synthesis of Methyl Orange and Its Application to Textiles
25Analysis of Natural Products
26Using a Gas Chromatograph: Identifying an Unknown Compound

Experiment 2 from Organic Chemistry with Vernier Lab Book

<i>Organic Chemistry with Vernier</i> book cover

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