ACETIC ACID. CH,COOH. The sour prin ciple of vinegar, an acid composed chemically of carbon, hydrogen, and oxygen. The commer cial acid is largely used in the manufacture of acetates, dye-stuffs, etc. Concentrated acetic acid burns the skin, and is therefore applied as a caustic to remove small warts and corns. Like any other acid, if taken internally for any length of time, dilute acetic acid impairs the digestion and absorption of food.
Acetic acid occurs here and there in the organic world. It is found ready formed in sweat and other animal secretions, as well as in the juices of various plants. It is manufactured either by the oxidation of ordinary alcohol through fermentation (see VINEGAR) , or by the destructive distillation of wood. The aqueous product obtained in the latter process is sub jected to fractional distillation, and the fraction constituting impure acetic acid (called pyrolig ?icons acid) is neutralized with soda or lime. In this manner a solution of sodium or calcium acetate is obtained; this solution is evaporated to dryness. and the remaining salt is freed from water and organic impurities by heating above 400° F. Pure acetic acid is prepared by dis tilling the acetates thus obtained with strong sulphuric acid. The pure anhydrous acid is known
as glacial acetic acid; at temperatures below 62° F. it is solid and crystalline; above that temperature it forms a colorless liquid readily known by its pungent, penetrating odor. Since carbon is one of its constituent elements, it is. of course, classed with the compounds of organic chemistry. It is a comparatively weak acid, its salts being broken up not only by the strong mineral acids, but even by many organic acids. Besides the methods just mentioned, acetic acid can be made by synthesis from the constit uent elements. When electric sparks are passed between carbon poles in an atmosphere of hydro gen, acetylene gas is produced: and when oxygen (furnished, say, by chromic acid) is made to act upon acetylene in the presence of water, the acetylene combines with oxygen and water, and, as a result, acetic acid is formed according to the following chemical equation: + 0 + 1120 = Acetylene Acetic acid It would not pay, however, to use this method in manufacturing acetic acid for practical pur poses.