Acetic acid (GAA, CAS 64-19-7), also known as glacial acetic acid in its concentrated form, is one of the most widely used organic acids in industry. The short answer to the question is yes: acetic acid is classified as a hazardous material under most national and international chemical management systems. This article explains why it is hazardous, how it is classified, and how it should be stored, handled, transported and disposed of safely.
What Is Acetic Acid (GAA CAS 64-19-7)?
Acetic acid is a colorless, transparent liquid with a pungent, vinegar-like odor. Its chemical formula is CH3COOH and its molecular weight is 60.05 g/mol. The term GAA stands for glacial acetic acid, which refers to concentrated acetic acid with a purity of 99.5% or higher. It is a fundamental building block for the chemical industry, used to produce vinyl acetate monomer, acetic anhydride, acetate esters and purified terephthalic acid (PTA), among many other products. Because of its acidity, it is also used in food processing as a preservative and acidulant, although food applications normally use dilute solutions rather than the glacial form.
Why Is Acetic Acid Considered Hazardous?
Acetic acid is hazardous for two principal reasons: corrosivity and flammability. Concentrated glacial acetic acid is strongly corrosive to skin, eyes and respiratory tissues, causing severe burns on contact. Its vapors are irritating and can damage the upper respiratory tract when inhaled. In addition, acetic acid is a combustible liquid: its vapors form explosive mixtures with air within a range of approximately 4% to 17% by volume. These combined hazards are why national chemical inventories, such as the Catalog of Hazardous Chemicals in China, list glacial acetic acid as a hazardous chemical requiring regulated management.
Hazard Classification and Transport Numbers
Under the Globally Harmonized System (GHS), glacial acetic acid carries the hazard statements H226 (flammable liquid and vapor) and H314 (causes severe skin burns and eye damage). In transport regulations such as the UN Recommendations on the Transport of Dangerous Goods, acetic acid is assigned to Class 8, corrosive substances. The specific UN number depends on concentration: glacial acetic acid with more than 80% acid is UN 2789, while aqueous solutions containing between 10% and 80% acid are assigned UN 1848. Both entries require corrosive labeling and, where applicable, the subsidiary flammable liquid risk class.
Key Physical and Chemical Properties
| Property | Typical Value |
|---|---|
| Molecular formula | C2H4O2 (CH3COOH) |
| Molecular weight | 60.05 g/mol |
| Appearance | Colorless transparent liquid |
| Density (20 °C) | Approximately 1.049 g/cm3 |
| Boiling point | Approximately 118 °C |
| Melting point | Approximately 16.6 °C |
| Flash point (open cup) | Approximately 57 °C |
| Explosive range in air | 4% to 17% by volume |
| pH of 6% aqueous solution | About 2.4 |
Note that glacial acetic acid freezes at about 16.6 °C, which is close to typical warehouse temperatures in winter. Storage areas should therefore be kept above this temperature, or thawing procedures should be planned for solidified material.
Safe Storage, Handling and Transport
Acetic acid should be stored in dedicated tanks or containers made of compatible materials such as stainless steel or approved plastics, in a cool, dry and well-ventilated area away from heat sources and open flames. It must be kept separate from strong oxidizers, strong bases and reactive metals. Containers must be clearly labeled with the product name, hazard pictograms and appropriate warning statements. Personnel who handle acetic acid should wear chemical-resistant gloves, protective clothing, safety goggles or a face shield, and use local exhaust ventilation. During transport, the product must be carried in approved packaging bearing the correct UN number and hazard labels, and operators should be trained in emergency response procedures.
Disposal and Emergency Response
Waste acetic acid must be treated as hazardous waste and handed to licensed waste management companies. It should never be poured into drains or released into the environment without neutralization and treatment. In the event of a spill, evacuate the area, ventilate, and contain the liquid with inert absorbents such as sand or vermiculite; small spills can be carefully neutralized with sodium bicarbonate under controlled conditions. For skin contact, remove contaminated clothing and rinse the affected area with plenty of water for at least 15 minutes, then seek medical attention. For eye contact, flush with water continuously and consult a physician immediately.
Frequently Asked Questions
Is acetic acid considered a hazardous material? Yes. Concentrated acetic acid (GAA) is classified as a hazardous chemical because it is corrosive and flammable. It is regulated under national hazardous chemical catalogs and international transport rules.
What is the difference between UN 2789 and UN 1848? UN 2789 covers glacial acetic acid and solutions with more than 80% acid, while UN 1848 covers acetic acid solutions containing between 10% and 80% acid. Both are Class 8 corrosive substances.
What personal protective equipment is needed when handling GAA? Chemical-resistant gloves, protective clothing, safety goggles or a face shield, and respiratory protection for situations with poor ventilation or high vapor concentrations.
Can acetic acid vapors form explosive mixtures? Yes. Acetic acid vapor mixed with air is explosive in the range of about 4% to 17% by volume, so sources of ignition must be excluded from storage and handling areas.
How should glacial acetic acid be stored in winter? Because glacial acetic acid freezes at about 16.6 °C, storage areas should be maintained above this temperature, or thawing procedures should be planned for solidified material.
What should be done if acetic acid is spilled? Evacuate and ventilate the area, contain the spill with inert absorbents, neutralize small amounts carefully with sodium bicarbonate, and dispose of the contaminated material as hazardous waste.
