What Is Acetic Acid?
Acetic acid is an organic compound registered under CAS number 64-19-7 with the molecular formula CH3COOH. It is a colorless liquid with a distinctive sour taste and a pungent, penetrating smell. In diluted form it is the main characterizing component of household vinegar, which typically contains 4 to 8 percent acetic acid in water. In concentrated form, acetic acid with very low water content is called glacial acetic acid.
| Property | Typical value |
|---|---|
| Molecular formula | CH3COOH |
| CAS number | 64-19-7 |
| Molecular weight | about 60.05 g/mol |
| Density | about 1.05 g/cm³ |
| Boiling point | about 118 °C at atmospheric pressure |
| Melting point | about 16.6 °C |
| Flash point (pure liquid) | about 39 °C |
| Solubility | Completely miscible with water and most organic solvents |
Because its melting point is about 16.6 degrees Celsius, pure acetic acid can solidify into an ice-like solid in cool environments, which is how glacial acetic acid got its name. In water it behaves as a weak acid that can donate a hydrogen ion in chemical reactions, and commercial material is supplied both as glacial acetic acid and as aqueous solutions of defined concentration.
Main Functions: Vinyl Acetate Monomer and Acetate Esters
The most important industrial function of acetic acid is as a building block for synthesizing a broad range of chemical compounds. Vinyl acetate monomer, abbreviated VAM, is produced from acetic acid and is a key raw material for paints, adhesives and plastics. Acetate esters such as ethyl acetate and butyl acetate are also made from acetic acid and are widely used in inks, coatings and cosmetics. In addition, acetic acid serves as a solvent and a pharmaceutical raw material in medicine production.
pH Regulation, Solvent and Dye Manufacturing
Acetic acid plays a key role as a pH regulator, fine-tuning the acidity of chemical reactions, particularly in dye and pigment manufacturing where a controlled acidic environment determines color yield and reproducibility. It is also an effective organic solvent used in the plastics, rubber and printing industries. In food applications, vinegar is the best-known use of acetic acid, employed for flavoring, pickling and food preservation. This versatility across chemistry, manufacturing and food processing makes it one of the most widely traded organic acids.
Metal Pickling and Industrial Cleaning
In metal processing, acetic acid solution is used for pickling, where it removes rust and oxide layers from metal surfaces before galvanizing, plating or painting. Because it dissolves oxide scale without being as aggressive as strong mineral acids, it is often chosen where a gentler treatment is required or where the risk of over-pickling the base metal must be kept low. Process parameters such as concentration, temperature and contact time are normally fixed by the finisher to suit the specific alloy and surface condition.
Safe Handling, Storage and Purchasing Notes
Glacial acetic acid is corrosive and can cause severe burns on skin contact; wear chemical-resistant gloves, goggles and protective clothing.
Vapors can irritate the eyes and respiratory tract, so the material should be used in well-ventilated areas.
The pure liquid has a flash point of about 39 degrees Celsius and must be stored away from open flames, heat and oxidizing agents.
Use containers made of compatible materials, such as stainless steel or suitable plastics, and keep them closed when not in use.
Specify concentration and grade clearly on the purchase order, for example glacial, technical solution or food grade, and request a certificate of analysis per lot.
On contact, rinse with plenty of water and seek medical attention if irritation persists.
Frequently Asked Questions
Q: What is the main function of acetic acid solution?
Its main function is as a chemical building block for producing vinyl acetate monomer and acetate esters; it also works as a solvent, pH regulator and pickling agent in many industries.
Q: Is acetic acid the same as vinegar?
Vinegar is a diluted solution that contains acetic acid as its main active component. Household vinegar typically contains 4 to 8 percent acetic acid dissolved in water.
Q: What is glacial acetic acid?
Glacial acetic acid is concentrated acetic acid with a very low water content. It is called glacial because it freezes into an ice-like solid at about 16.6 degrees Celsius.
Q: Is acetic acid used in food?
Yes. In the form of vinegar it is widely used in cooking, pickling and food preservation, and diluted acetic acid is an approved food ingredient in many countries.
Q: Why is acetic acid used for pickling metals?
It dissolves rust and oxide layers on metal surfaces without being as aggressive as strong mineral acids, which makes it suitable for cleaning metal before galvanizing, plating or painting.
Q: What is the CAS number of acetic acid?
The CAS registry number of acetic acid is 64-19-7, and its molecular formula is CH3COOH.