how to prepare glacial acetic acid

How to Prepare Glacial Acetic Acid

Glacial acetic acid is a pure form of acetic acid, boasting a high concentration of about 99-100%. It is a key chemical compound widely used in various industries, including food preservation, production of plastics, and as a solvent for different chemical processes. Preparing glacial acetic acid requires careful handling and adherence to safety protocols due to its corrosive nature. Here’s a guide on how to prepare glacial acetic acid through a laboratory-scale process.

Materials Needed

1. Reactants - Ethanol (C2H5OH) - Sodium dichromate (Na2Cr2O7) - Sulfuric acid (H2SO4)

2. Equipment - Round-bottom flask - Distillation apparatus - Heating mantle or hot plate - Thermometer - Condenser - Ice bath

Procedure

1. Setup Begin by setting up your distillation apparatus. Attach the round-bottom flask to the condenser, ensuring that all connections are airtight. Place an ice bath beneath the condenser to facilitate the cooling of vapors.

2. Reaction Mixture In the round-bottom flask, mix ethanol and sodium dichromate in a stoichiometric ratio (generally, a 31 ratio of ethanol to sodium dichromate). The sodium dichromate acts as an oxidizing agent, promoting the oxidation of ethanol to acetic acid.

3. Add Sulfuric Acid Carefully add sulfuric acid to the reaction mixture. The addition should be done slowly to control the exothermic reaction and prevent splattering. The presence of sulfuric acid catalyzes the reaction and enhances the yield of acetic acid.

4. Heating Heat the reaction mixture gradually using a heating mantle or hot plate. Monitor the temperature to ensure it remains at a level conducive to the reaction, typically around 60-80°C.

5. Distillation As the reaction proceeds, acetic acid will begin to vaporize. The vapor travels through the condenser, where it cools and condenses back into liquid form. Collect the condensed liquid acetic acid in a clean receiving flask.

6. Purification The acetic acid collected may still contain residual water and impurities. To purify it further, use simple distillation. Heating the liquid at a temperature above 100°C will help separate water from the acetic acid due to their different boiling points.

7. Storage Once you obtain concentrated acetic acid, store it in a well-sealed glass container labeled Glacial Acetic Acid. Ensure it is kept in a cool, dry place away from sunlight and incompatible substances.

Safety Precautions

When preparing glacial acetic acid, wear appropriate personal protective equipment (PPE), including gloves, goggles, and a lab coat. Work in a well-ventilated area or fume hood to prevent inhalation of vapors. Always be cautious with the chemicals involved and follow all safety guidelines.

In summary, preparing glacial acetic acid involves careful mixing and distillation of ethanol with an oxidizing agent. Despite its efficiency, safety must always be the top priority in any chemical preparation.