Ethanoic acid, also called acetic acid, is a chemical with a sharp, acrid smell. You may recognize the smell as being similar to vinegar. Considered a weak synthetic acid, acetic or ethanoic acid is still a powerful chemical. Ethanoic acid has many uses in industrial, medical and household settings.

Acetic or ethanoic acid is a weak carboxylic acid. The chief acetic acid formula is C₂H₄O₂. The acetic acid formula represents two carbons, four hydrogens and two oxygens. Another way of expressing the acetic acid formula is CH₃COOH. This better demonstrates its carboxyl group (-COOH). Acetic acid forms when ethanol is combined with oxygen in the air, yielding ethanoic (acetic) acid and water. This is called the oxidation of ethanol.

Ethanoic acid has no color, but it has a sharp, strong odor very much like vinegar. Keep in mind this is a flammable chemical, with a flashpoint of 39 degrees Celsius or 104 degrees Fahrenheit. Its boiling point is 118 degrees Celsius. Acetic acid is designated as a volatile organic compound.

Acetic acid absorbs moisture, so it is classified as hygroscopic. It can react powerfully with either bases or acids. Acetic acid at high concentrations will also corrode metal and degrade plastics and rubber. Other acetic acid common names include vinegar acid, ethylic acid, methanecarboxylic acid, glacial acetic acid and glacial ethanoic acid.

Fermenting fruits make acetic acid naturally. Some bacteria also excrete it, such as the highly common Acetobacter organisms. There are several methods for making acetic acid artificially, such as methanol carbonylation and methyl acetate carbonylation.

Numerous acetic acid uses exist across multiple arenas. In industry, there are broad uses for ethanoic or acetic acid. It commonly serves as a chemical reagent in laboratories, but also on a larger industrial scale. In chemical companies, acetic acid is used to make other chemicals.

Acetic acid is used in the manufacture of plastic items such as bottles other synthetic materials. Ethanoic or acetic acid is used in making dyes, pigments, and paint and coating additives. It is used in printing on fabric. It is a component of wood glue and other sealants. Acetic acid is also used as a cleaning and degreasing solvent. It can be used to etch inorganic films. Acetic acid is commonly used in photographic materials such as film and chemical solutions. It is also used in the petroleum industry and is used to plate and treat surfaces, such as on cars. Acetic acid is also used in the production of pharmaceuticals.

In the food industry, acetic acid in lower concentrations is used as a food additive, flavoring and preservative. Acetic acid regulates food acidity.

In the household, food acetic acid uses include pickling and the acid's presence in vinegar. Pickling vegetables and fruits with vinegar preserves them because acetic acid prevents bacterial growth. Diluted acetic acid is prevalent in some window cleaning sprays and other household cleaners. Laundry and dishwashing detergents also often carry acetic acid. Acetic acid is a component of anti-freeze and de-icing agents, and it is used in pest-control agents like herbicides and insecticides. It is a component of some car polishes. Even makeup and vitamins are often made with acetic acid!

In medicine, there are interesting acetic acid uses, some of which have endured for centuries. Acetic acid is an ingredient of wart remover solutions. It can also be found in some eardrops. Acetic acid possesses both antifungal and antibacterial benefits.

In lower concentrations, acetic acid has been used as a topical agent to treat wounds, especially burn wounds. Acetic acid helped prevent the spread of the bubonic plague. It was even crucial in helping the injured during the Civil War. Dilute acetic acid is effective at fighting some resistant strains of bacteria. It has also been proven to be an effective treatment against pernicious fungal infections. In particular, sufferers of the disease mucormycosis, an often-fatal disease caused by fungi in the Mucorales order, may benefit from low-dose applications of acetic acid. Expensive and invasive treatments have historically been used to fight this kind of infection. This fungal infection does not respond to other kinds of acid such as lactic and hydrochloric acid. But at a 0.3 percent concentration, dilute acetic acid inhibits fungal spore germination. Acetic acid seems to work because of both hydrogen ion concentration as well as free acetate in fungal cells. The appeal of using ethanoic or acetic acid as an antifungal agent is crucial. It is a relatively inexpensive chemical and readily available. It can be kept at a stable temperature. At low concentrations, it is not as harmful as at higher industrial concentrations. Topical acetic acid can therefore be used effectively in the field or in remote regions, particularly war zones to treat the wounded. If treated early with this topical acetic acid, wounds may not be as severe.

In addition to its antifungal capability, acetic acid serves as an antibacterial treatment as well. Burn wounds often become infected, and many antiseptic treatments can harm healing skin and even disrupt healthy repair. One of the worst offending bacteria that infect burn wounds is Pseudomonas aeruginosa. This bacterium is infamous for having several strains that are resistant to antibiotics and antiseptics. Those who suffer from its infections risk long and expensive hospital stays. In scenarios of antibiotic-resistant bacteria, dilute acetic acid once again proves to be an effective and inexpensive option. Effective acetic acid concentrations range from 0.5 to 5 percent. This concentration works against several antibiotic strains of P. aeruginosa, making it another excellent medical tool for hospitals to use for soft tissue and burn wounds.

Despite the beneficial uses of ethanoic acid, it poses risks to health that must be considered when handling it. Protective clothing and eyewear must be worn at all times around concentrated ethanoic acid. Work areas must be properly ventilated, and breathing protection is necessary. The temperature must be kept well below the flashpoint of 39 degrees Celsius to prevent an explosive vapor and air mixture. Electrical equipment also needs protection. Even at a lower temperature of 20 degrees Celsius, acetic acid fumes can contaminate the air.

Ethanoic or acetic acid is highly corrosive, so inhaling it can damage the tender linings of the lungs, nose and throat. Breathing ethanoic or acetic acid can also lead to worse symptoms such as shortness of breath, dizziness and lung edema. Ethanoic or acetic acid must never be ingested. It can cause chemical burns and blisters on unprotected skin after only a few minutes. Highly concentrated acetic acid can damage the cornea of the eye as well, and that can result in vision loss.

At high concentrations, ethanoic or acetic acid is harmful to species of plants and animals. One fortunate aspect of acetic acid is that it is soluble in water, and it degrades quickly into compounds that are not as detrimental. Ethanoic acid is, however, an emission pollutant from the paper, chemical and textiles industries. It can also be produced as a result of mining.