acetic acid

acetic acid

a colourless pungent liquid, miscible with water, widely used in the manufacture of acetic anhydride, vinyl acetate, plastics, pharmaceuticals, dyes, etc. Formula: CH₃COOH

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

acetic acid

[ə′sēd·ik ′as·əd]

(organic chemistry)

CH₃COOH

A clear, colorless liquid or crystalline mass with a pungent odor, miscible with water or alcohol; crystallizes in deliquescent needles; a component of vinegar. Also known as ethanoic acid.

A mixture of the normal and acetic salts; used as a mordant in the dyeing of wool.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Acetic Acid

 

CH₃COOH, a monobasic carboxylic acid of the aliphatic series. Acetic acid is a colorless liquid with a pungent odor and an acid taste. Anhydrous, or glacial, acetic acid has a melting point of 16.75°C, a boiling point of 118.1°C, and a density of 1.055 g/cm³ at 15°C. Acetic acid is miscible with water, alcohol, ether, benzene, and many other organic solvents. It is not soluble in carbon disulfide, but it readily dissolves many inorganic and organic substances, including sulfur, phosphorus, hydrogen halides, and cellulose acetate. Acetic acid is a weak acid, with a dissociation constant K = 1.75 × 10^–5. It forms such typical derivatives of carboxylic acids as salts and esters, called acetates, an anhydride, an acid halide, amides, and anilides.

Acetic acid, in the form of vinegar, was the first acid known to man. It is widespread in nature both in free form and in the form of salts and esters, and it is formed during putrefaction and fermentation. There are four main industrial methods of preparing acetic acid: (1) oxidation of acetaldehyde by exposure to air or oxygen at 60°C in the presence of manganese acetate [(CH₃COO)₂Mn]; (2) pyrolysis of acetone with subsequent hydration of the resulting ketene

(3) oxidation of individual hydrocarbons, such as butane or benzine fractions; and (4) reaction of methanol with carbon monoxide. Another method, still of some importance, is the extraction of acetic acid from wood vinegar, one of the products obtained from the dry distillation of wood. The acetic acid in vinegar is obtained by the acetic fermentation of alcoholic liquids.

In industry, acetic acid, together with acetic anhydride and acetyl chloride, is used for introducing the acetyl radical (CH₃CO—)—a process known as acetylation—in, for example, the preparation of the esters used as perfumes, solvents, and pharmaceuticals (acetylsalicylic acid, phenacetin). Salts of acetic acid are used in the preparation of pigments (acetates of lead and copper); other salts are used as catalysts (acetates of manganese, cobalt, zinc), and as mordants in dyeing (basic salts of acetic acid).

Acetic acid vapors irritate the mucosa and, in particular, the eyes; the permissible concentration of the vapors in the air is 0.005 milligram per liter. Concentrated (more than 30 percent) solutions of acetic acid cause burns upon contact with the skin.

V. N. FROSIN

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.