ACETIC ACID, the soar principle in vinegar, is the most common of the vegetable acids. If alcohol, diluted with water, be mixed with a ferment, such as yeast, and ex posed to the air at, or a little above, its ordinary temperature, it is rapidly converted into vinegar or A. A. The change is accompanied by the absorption of oxygen, two atoms of which combine with as many of hydrogen to form water, whilst other two hike the place of the hydrogen which has become water, so that A. A. is produced from alcohol by the substitution of two atoms of oxygen for two of hydrogen. Thus alcohol is C411602. If we take front this two atoms of hydrogen, and add two of oxygen, it becomes But from the mode in. which A. A. acts when it combines with bases, it is cer tam that one of the equivalents of hydrogen and one of oxygen are united as water, so that the formula of A. A. is HO. A striking experiment may be made illus trating the mode in which alcohol is converted into A. A. If slightly diluted alcohol be dropped upon platinum-black, the oxygen condensed in that substance acts with great energy on the spirit, and A. A. is evolved in vapor. Here the whole office of platinum
is to determine the oxygen of the air, and the hydrogen of the alcohol to unite. In the commercial processes for manufacturing vinegar, some vegetable substance containing nitrogen (one of the albuminous principles) takes the place of the platinum-black, and determines the same change. A. A. is not known in the anhydrous form. In its most concentrated state it contains an equivalent of water, + ITO. When it com bines with metallic oxides, they take the place of the water; acetate of soda, for example, consisting of soda and anhydrous A. A., The salts of A. A., called ACETATES, arc numerous and important in the arts. The most important is ace tate or sugar of lead. See LEAD. For the commercial processes of manufacturing A. A., R.