Glacial acetic acid is the pure form of acetic acid, which is the main component of vinegar. Glacial acetic acid has a very low water content (less than 1%) and a high freezing point of 16.7 °C, which makes it solidify into ice-like crystals at slightly lower temperatures. Glacial acetic acid is also a corrosive and pungent liquid that can injure skin on contact, so it should be handled with care and proper protection.
In this article, we will explain how to make glacial acetic acid from vinegar using a simple distillation process. We will also discuss some of the uses and properties of glacial acetic acid.
Materials and equipment
To make glacial acetic acid, you will need the following materials and equipment:
- Vinegar (at least 4% acetic acid by volume)
- Baking soda (sodium bicarbonate)
- Distillation apparatus (flask, condenser, thermometer, receiver)
- Heating source (hot plate or Bunsen burner)
- Ice bath
- Glass jar with lid
- pH paper or indicator
- Safety goggles, gloves and apron
Procedure
- Measure 500 mL of vinegar and pour it into a flask. Add a few drops of pH indicator or a piece of pH paper to monitor the acidity of the solution.
- Add baking soda gradually to the vinegar while stirring until the pH indicator or paper shows a neutral or slightly basic reaction (pH around 7 or 8). This will neutralize the excess acid in the vinegar and form sodium acetate, which is more soluble in water than acetic acid.
- Set up the distillation apparatus by connecting the flask to the condenser and the condenser to the receiver. Place the thermometer in the flask and the receiver in an ice bath. Make sure there are no leaks in the connections.
- Heat the flask gently until the solution starts to boil. The temperature should be around 118 °C, which is the boiling point of acetic acid. The acetic acid will vaporize and condense in the receiver, while the water and sodium acetate will remain in the flask.
- Collect the distillate in the receiver until no more liquid comes out of the condenser. You should obtain about 100 mL of acetic acid solution.
- Transfer the acetic acid solution to a glass jar and seal it tightly. Store it in a cool and dark place for a few days to allow any remaining water to separate from the acetic acid.
- Carefully decant or siphon off the upper layer of acetic acid from the lower layer of water. You should obtain about 50 mL of glacial acetic acid with a concentration of over 99%.
- Dispose of the waste materials according to safety regulations.
Uses and properties
Glacial acetic acid is an important organic reagent that has many applications in chemistry, biology, medicine and industry. Some of its uses are:
- As a solvent for organic compounds such as esters, alcohols, ketones and ethers
- As a catalyst for reactions such as esterification, hydrolysis and polymerization
- As a preservative for food and beverages
- As a coagulant for proteins and latex
- As a disinfectant and antiseptic for wounds and infections
- As a dyeing agent for textiles and leather
- As a component of photographic chemicals and explosives
Glacial acetic acid is also a weak acid that can donate a proton to form acetate ions. It has a pKa value of 4.76, which means that it is partially dissociated in aqueous solutions. The acidity of glacial acetic acid depends on its concentration and temperature. At higher concentrations and lower temperatures, glacial acetic acid forms dimers that are linked by hydrogen bonds, which reduce its ability to ionize.
Glacial acetic acid has some physical properties that are different from those of regular acetic acid or vinegar. Some of them are:
- Density: 1.049 g/mL (liquid); 1.27 g/mL (solid)
- Melting point: 16.7 °C
- Boiling point: 118 °C
- Viscosity: 1.22 mPa s
- Refractive index: 1.371
- Dipole moment: 1.74 D
Conclusion
Glacial acetic acid is a pure form of acetic acid that has many uses and properties. It can be made from vinegar by neutralizing it with baking soda and distilling it to remove water and impurities. Glacial acetic acid is a corrosive and pungent liquid that should be handled with care and proper protection.
Extended Reading:
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