ACETIC ACID. 79 



acid when left in contact with the air. In this manner 

 vinegar is formed, which is a mixture of acetic acid 

 with a great deal of water and small quantities of acci- 

 dental foreign substances. 



It is obtained by allowing wine, beer, fermented 

 fruit juices, particularly after the addition of a small 

 quantity of vinegar, to acidify spontaneously, in vessels 

 which permit the access of air and are kept warm. Or 

 by a similar acidifying of fermented beer wort, or ot 

 mixtures of brandy arid water with honey and a fer- 

 ment. This takes place most readily in the German 

 process for the manufacture of vinegar (Schnellessigfa- 

 brikation)," in which the liquid to be acidified is ex- 

 posed to the air in such a manner that as much surface 

 as possible may be presented to its action. This is 

 effected by allowing the liquid to flow slowly through 

 a high cask filled with .beech shavings, the sides of the 

 cask being furnished with air holes. The shavings 

 must be previously steeped in vinegar. 



By distilling vinegar the acetic acid can be freed 

 from the foreign substances with which it is mixed, 

 but the water cannot be removed by this means. 



The anhydrous acid is obtained by distilling 5 parts 

 anhydrous sodium acetate with 6 parts concentrated 

 sulphuric acid, or also by distilling an intimate mixture 

 of equal parts of anhydrous lead acetate and fused 

 potassium bisulphate. 



A large quantity of acetic acid is obtained by the 

 destructive distillation of wood (wood vinegar). The 

 watery distillate is saturated with sodium carbonate, 

 evaporated, the dried sodium salt heated for a length 

 of time at 230-250 for the purpose of destroying any 

 organic impurities which may be present, dissolved in 

 water, filtered, evaporated and the heating repeated if 

 necessary. 



Properties. Colorless liquid of a penetrating and 

 pleasant acid odor, of a sharp acid taste, caustic ; 

 specific gravity, 1.056 at 15.5 ; fumes slightly in the 

 air ; boils at + 119 ; its vapor is inflammable and burns 

 with a blue flame. It crystallizes in lustrous, transpa- 

 rent tablets, which fuse at +17. Miscible with 

 water in all proportions. At first the specific gravity 



