CHAPTER II 



THE ACIDS 



A. DISCOVERY OF THE COMMON ACIDS 



Vegetable acids. The earliest acids known were of 

 vegetable origin, but until the middle of the eighteenth 

 century scarcely any attempt was made to isolate them from 

 the "sour" liquids in which they occur, or even to distinguish 

 between various acids of similar origin. The most familiar 

 of the vegetable acids was sour wine or VINEGAR, which 

 was known to have a remarkable action upon soda 

 (Chapter I. p. 4). Its power of dissolving chalky materials is 

 illustrated by the story of Cleopatra and the pearls which 

 she dissolved and drank in a cup of vinegar, as well as by 

 Livy's fantastic story of the use of vinegar by Hannibal to 

 dissolve away the limestone rocks of the Alps. DISTILLED 

 VINEGAR was familiar to the alchemists from the time of 

 Geber, and was frequently used as a solvent, but it was not 

 until a much later period that the acid constituent, ACETIC 

 ACID, was isolated in a pure state. 



A large number of crystalline acids of animal and vegetable 

 origin were, however, prepared at the close of the eighteenth 

 century by the Swedish chemist, Carl Wilhelm Scheele, 

 (1742-1786), whose work on these substances may be 



