Acetic acid

Acetic acid (systematically named ethanoic acid, also methanecarboxylic acid)
Chemical formula : C₂H₄O₂ (also written as CH3CO2H or CH3-COOH).
(O = 53,29 %, C = 40 %, H = 6,71 %)

Molar mass = 60,052 ± 0,0025 g·mol^-1

Glacial acetic acid is a trivial name for water-free (anhydrous) acetic acid, the name comes from the ice-like crystals that form slightly below room temperature at 16.6 °C (61.9 °F) [the presence of 0.1% water lowers its melting point by 0.2 °C]. It ispresent in the vinegar naturally, he gives his sour taste and pungent smell (detectable from 1 ppm22).

Acetic acid is one of the simplest carboxylic acids (as examples: methanoïc acid, formic acid, -secreted by certain ants, propanoïc acid, propionic acid, butanoïc acid, etc.).. It is an important chemical reagent and industrial chemical, mainly used in the production of cellulose acetate for photographic film and polyvinyl acetate for wood glue, as well as synthetic fibers and fabrics.
The hydrogen center in the carboxyl group (-COOH) in carboxylic acids such as acetic acid can separate from the molecule by ionization:

Because of this release of the proton (H+), acetic acid has acidic character. Acetic acid is a weak monoprotic acid. In aqueous solution, it has a pKa value of 4.76. Its conjugate base is acetate (CH3COO^-). A 1.0 M solution (about the concentration of domestic vinegar) has a pH of 2.4, indicating that merely 0.4% of the acetic acid molecules are dissociated.

Acetic acid is also present in the environment. Many plants contain and can thus identify as volatile issue. The thermal degradation of the wood product. It is found in many foods as an added ingredient or as a natural component. Human activity can also be a source of acetic acid emission in the atmosphere, including, among others, the vehicle exhaust and combustion plants, plastics and other waste.

Acetic acid is produced and excreted by acetic acid bacteria, notable ones being the Acetobacter genus and Clostridium acetobutylicum. These bacteria are found universally in foodstuffs, water, and soil, and acetic acid is produced naturally as fruits and other foods spoil.

Production.
Industrially, it is produced in 75% acetic acid for the chemical industry acid by carbonylation of methanol. Also by oxidation of acetaldehyde or by liquid phase oxidation of n-butane C₄H₁₀, or it is recovered in the production of cellulose acetate or polyvinyl alcohol (CH2-CHOH) n. It can be prepared from ethylene (Wacker or Showa Denko processes). Acetic acid may be produced synthetically or by bacterial fermentation. Today, the biological method is no longer about 10% of production, but it remains important for the production of vinegar, because in most countries the law provides that the vinegar for food must be of biological origin.
As of 2003–2005, total worldwide production of virgin acetic acid was estimated at 5 Mt/a (million tonnes per year), approximately half of which was then produced in the United States. European production stood at approximately 1 Mt/a and was declining, and 0.7 Mt/a were produced in Japan. Another 1.5 Mt were recycled each year, bringing the total world market to 6.5 Mt/a.
Since then the global production has increased to 10.7 Mt/a (in 2010), and further, however, slowing increase in production is predicted.[

Main features :
Pure acetic acid is a colorless, flammable, hygroscopic liquid, and very poor conductor.
These properties of the solvent and miscibility of the acid form is widely used in the chemical industry.
It is corrosive to many metals, including iron, magnesium and zinc. It forms dihydrogen and metal salts called acetates. The aluminum shape in contact with a thin layer of oxygen relatively resistant aluminum oxide, which covers its surface: aluminum tanks are often used to carry acetic acid.

	Product
Density  (liquid)	1049 kg/m3
Melting point	16 to 17 °C (61 to 62 °F)
Boiling point	118 to 119 °C (391 to 392 K)
Viscosity	1.22 mPa s
Acidity (pKa)	4.76

(at 25 °C (77 °F), 100 kPa)

Commercial solutions.

• aqueous solution of 3 to 10% (weight/weight or w /w)
• aqueous solution to more than 10 and less than 80% (w/w)
• aqueous solution at 80% (w/w)

In water treatment, it is used by injection in the form of water diluted reagent (diluted to 5% by volume solutions, from 75% acid).

NOTE:
Impurities that can be detected in acetic acid solutions depend on the process used to produce glacial acetic acid.
It can detect small amounts of acetaldehyde, acetic anhydride, formic acid, diacetyl, methyl acetate, ethyl acetoacetate, iron, mercury, iodine, bromine and chlorides.

A formulation for water treatment.
Reaction mechanism of calcium bicarbonates (simplified equations):

With 1 mg / l (or 1 g/m3) CH₃COOH added, there is (10/120) = 0.08 °f lower TAC (alkalinity), and it is formed 0.74 mg of free CO2, and 0.98 mg of CH3COO-acetate.

Storage.
Choosing a type of container must comply with the code of flammable and combustible liquids, the maximum capacity of containers and portable tanks for flammable or combustible liquids are different depending on the type of container.
A store (link) in an airtight container kept closed, wearing a clear identification of its contents, placed in a cool, dry, well-ventilated area, away from bases and other incompatible materials.
Store in a place with cement floor resistant to corrosion. Reservoirs and tanks corrosive liquid must be equipped with an overfill device.
Usually stored in stainless steel containers or high-density polyethylene and polypropylene.

Uses :

• Treatment of waste water or industrial (as dilute aqueous solutions)
• As solvent: water-miscible and in various organic solvents such as ethanol, diethyl ether, but insoluble in glycérol19 sulfide carbone19, it is also a good solvent for the gums, resins, phosphorus, sulfur and 19 acids "halogen"
• Production of acetic anhydride, cellulose acetate, vinyl acetate monomer, and other acetates, as well as drugs, pesticides, dyes, the photography industry
• Supply (production of fruit vinegars, etc.), food additive
• Cleaning agent (semiconductor)
• Coagulant (natural latex)
• Bacteriostatic (in solution)
• Production of plastics such as polyethylene terephthalate (PET) or cellulose acetate useful for the production of vinyl acetate (paints, adhesives) and organic solvents.
• Additives in tobacco products (flavor).

Health effects and safety.
Concentrated acetic acid is corrosive to skin and must, therefore, be handled with appropriate care, since it can cause skin burns, permanent eye damage, and irritation to the mucous membranes. These burns or blisters may not appear until hours after exposure. Latex gloves offer no protection, so specially resistant gloves, such as those made of nitrile rubber, are worn when handling the compound. Concentrated acetic acid can be ignited with difficulty in the laboratory. It becomes a flammable risk if the ambient temperature exceeds 39 °C (102 °F), and can form explosive mixtures with air above this temperature (explosive limits: 5.4–16%).
Acetic acid is a strong eye, skin, and mucous membrane irritant. Prolonged skin contact with glacial acetic acid may result in tissue destruction.
Inhalation exposure (8 hours) to acetic acid vapours at 10 ppm could produce some irritation of eyes, nose, and throat; at 100 ppm marked lung irritation and possible damage to lungs, eyes, and skin might result. Vapour concentrations of 1,000 ppm cause marked irritation of eyes, nose and upper respiratory tract and cannot be tolerated. These predictions were based on animal experiments and industrial exposure.
Skin sensitization to acetic acid is rare, but has occurred. It has been reported that, 12 workers exposed for two or more years to an estimated mean acetic acid airborne concentration of 51 ppm, there were symptoms of conjunctive irritation, upper respiratory tract irritation, and hyperkeratotic dermatitis. Exposure to 50 ppm or more is intolerable to most persons and results in intensive lacrimation and irritation of the eyes, nose, and throat, with pharyngeal oedema and chronic bronchitis. Un acclimatized humans experience extreme eye and nasal irritation at concentrations in excess of 25 ppm, and conjunctivitis from concentrations below 10 ppm has been reported. In a study of 5 workers exposed for 7 to 12 years to concentrations of 80 to 200 ppm at peaks, the principal findings were blackening and hyperkeratosis of the skin of the hands, conjunctivitis (but no corneal damage), bronchitis and pharyngitis, and erosion of the exposed teeth (incisors and canines).

Toxicological profile (French) - Acide nitrique (FT 24) par l'Institut national de recherche et de sécurité (INRS).

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